CSS Color Module Level 3 (original) (raw)

Abstract

CSS (Cascading Style Sheets) is a language for describing the rendering of HTML and XML documents on screen, on paper, in speech, etc. It uses color-related properties and values to color the text, backgrounds, borders, and other parts of elements in a document. This specification describes color values and properties for foreground color and group opacity. These include properties and values from CSS level 2 and new values.

Status of This Document

This section describes the status of this document at the time of its publication. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.

This document was published by the CSS Working Group as a Recommendation using the Recommendation track.

A W3C Recommendation is a specification that, after extensive consensus-building, is endorsed by W3C and its Members, and has commitments from Working Group members to royalty-free licensing for implementations.

W3C recommends the wide deployment of this specification as a standard for the Web.

This document was produced by a group operating under the W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

This document is governed by the 2 November 2021 W3C Process Document.

A separate implementation report shows that each test in the test suite was passed by at least two independent implementations. However, most tests have now been updated for CSS Color 4 (seeimplementation report).

A complete list of changes to this document is available.

Table of Contents

1. Introduction

This section is non-normative.

CSS beyond level 2 is a set of modules, divided up to allow the specifications to develop incrementally, along with their implementations. This specification is one of those modules.

This module describes CSS properties which allow authors to specify the foreground color and opacity of an element. This module also describes in detail the CSS value type.

It not only defines the color-related properties and values that already exist in CSS1 and CSS2, but also defines new properties and values.

The specification is the result of the merging of relevant parts of the following Recommendations and Working Drafts, and the addition of some new features.

2. Dependencies

Additional terminology is defined in the Definitions section of [CSS21]. Examples of document source code and fragments are given in XML [XML10] or HTML [HTML401] syntax.

3. Color properties

3.1. Foreground color: the ‘color’ property

Name: color
Value: | inherit
Initial: depends on user agent
Applies to: all elements
Inherited: yes
Percentages: N/A
Computed value: The computed value for basic color keywords, RGB hex values and extended color keywords is the equivalent triplet of numerical RGB values, e.g. six digit hex value or rgb(...) functional value, with an alpha value of 1. The computed value of the keyword ‘transparent’ is the quadruplet of all zero numerical RGBA values, e.g. rgba(0,0,0,0). For all other values, the computed value is the specified value.

This property describes the foreground color of an element's text content. In addition it is used to provide a potential indirect value (currentColor) for any other properties that accept color values. If the ‘currentColor’ keyword is set on the ‘color’ property itself, it is treated as ‘color: inherit’.

There are different ways to specify lime green:

Example(s):

em { color: lime } /* color keyword / em { color: rgb(0,255,0) } / RGB range 0-255 */

Color units are defined in a following section.

3.2. Transparency: the ‘opacity’ property

Opacity can be thought of as a postprocessing operation. Conceptually, after the element (including its descendants) is rendered into an RGBA offscreen image, the opacity setting specifies how to blend the offscreen rendering into the current composite rendering. See simple alpha compositing for details.

Name: opacity
Value: | inherit
Initial: 1
Applies to: all elements
Inherited: no
Percentages: N/A
Computed value: The same as the specified value after clipping the to the range [0.0,1.0].

Syntactically a . The uniform opacity setting to be applied across an entire object. Any values outside the range 0.0 (fully transparent) to 1.0 (fully opaque) will be clamped to this range. If the object has children, then the effect is as if the children were blended against the current background using a mask where the value of each pixel of the mask is . For SVG, ‘has children’ is equivalent to being a container element [SVG11].

Since an element with opacity less than 1 is composited from a single offscreen image, content outside of it cannot be layered in z-order between pieces of content inside of it. For the same reason, implementations must create a new stacking context for any element with opacity less than 1. If an element with opacity less than 1 is not positioned, then it is painted on the same layer, within its parent stacking context, as positioned elements with stack level 0. If an element with opacity less than 1 is positioned, the ‘z-index’ property applies as described in [CSS21], except that if the used value is ‘auto’ then the element behaves exactly as if it were ‘0’. See section 9.9 andAppendix E of [CSS21] for more information on stacking contexts. The rules in this paragraph do not apply to SVG elements, since SVG has its own rendering model ([SVG11], Chapter 3).

4. Color units

A is either a keyword or a numerical specification.

4.1. Basic color keywords

The list of basic color keywords is: aqua, black, blue, fuchsia, gray, green, lime, maroon, navy, olive, purple, red, silver, teal, white, and yellow. The color names are ASCII case-insensitive.

Color names and sRGB values

Named Numeric Color name Hex rgb Decimal
black #000000 0,0,0
silver #C0C0C0 192,192,192
gray #808080 128,128,128
white #FFFFFF 255,255,255
maroon #800000 128,0,0
red #FF0000 255,0,0
purple #800080 128,0,128
fuchsia #FF00FF 255,0,255
green #008000 0,128,0
lime #00FF00 0,255,0
olive #808000 128,128,0
yellow #FFFF00 255,255,0
navy #000080 0,0,128
blue #0000FF 0,0,255
teal #008080 0,128,128
aqua #00FFFF 0,255,255

Example(s):

body {color: black; background: white } h1 { color: maroon } h2 { color: olive }

4.2. Numerical color values

4.2.1. RGB color values

The RGB color model is used in numerical color specifications. These examples all specify the same color:

Example(s):

em { color: #f00 } /* #rgb / em { color: #ff0000 } / #rrggbb */ em { color: rgb(255,0,0) } em { color: rgb(100%, 0%, 0%) }

The format of an RGB value in hexadecimal notation is a ‘#’ immediately followed by either three or six hexadecimal characters. The three-digit RGB notation (#rgb) is converted into six-digit form (#rrggbb) by replicating digits, not by adding zeros. For example, #fb0 expands to #ffbb00. This ensures that white (#ffffff) can be specified with the short notation (#fff) and removes any dependencies on the color depth of the display.

The format of an RGB value in the functional notation is ‘rgb(’ followed by a comma-separated list of three numerical values (either three integer values or three percentage values) followed by ‘)’. The integer value 255 corresponds to 100%, and to F or FF in the hexadecimal notation: rgb(255,255,255) = rgb(100%,100%,100%) = #FFF. White space characters are allowed around the numerical values.

All RGB colors are specified in the sRGB color space (see [SRGB]). User agents may vary in the fidelity with which they represent these colors, but using sRGB provides an unambiguous and objectively measurable definition of what the color should be, which can be related to international standards (see [COLORIMETRY]).

Values outside the device gamut should be clipped or mapped into the gamut when the gamut is known: the red, green, and blue values must be changed to fall within the range supported by the device. User agents may perform higher quality mapping of colors from one gamut to another. This specification does not define precise clipping behavior. For a typical CRT monitor, whose device gamut is the same as sRGB, the four rules below are equivalent:

Example(s):

em { color: rgb(255,0,0) } /* integer range 0 - 255 / em { color: rgb(300,0,0) } / clipped to rgb(255,0,0) / em { color: rgb(255,-10,0) } / clipped to rgb(255,0,0) / em { color: rgb(110%, 0%, 0%) } / clipped to rgb(100%,0%,0%) */

Other devices, such as printers, have different gamuts than sRGB; some colors outside the 0..255 sRGB range will be representable (inside the device gamut), while other colors inside the 0..255 sRGB range will be outside the device gamut and will thus be mapped.

4.2.2. RGBA color values

The RGB color model is extended in this specification to include “alpha” to allow specification of the opacity of a color. See simple alpha compositing for details. These examples all specify the same color:

Example(s):

em { color: rgb(255,0,0) } /* integer range 0 - 255 / em { color: rgba(255,0,0,1) / the same, with explicit opacity of 1 / em { color: rgb(100%,0%,0%) } / float range 0.0% - 100.0% / em { color: rgba(100%,0%,0%,1) } / the same, with explicit opacity of 1 */

Unlike RGB values, there is no hexadecimal notation for an RGBA value.

The format of an RGBA value in the functional notation is ‘rgba(’ followed by a comma-separated list of three numerical values (either three integer values or three percentage values), followed by an , followed by ‘)’. The integer value 255 corresponds to 100%, rgba(255,255,255,0.8) = rgba(100%,100%,100%,0.8). White space characters are allowed around the numerical values.

Implementations must clip the red, green, and blue components of RGBA color values to the device gamut according to the rules for the RGB color value composed of those components.

These examples specify effects that are possible with the rgba() notation:

Example(s):

p { color: rgba(0,0,255,0.5) } /* semi-transparent solid blue / p { color: rgba(100%, 50%, 0%, 0.1) } / very transparent solid orange */

Note. If RGBA values are not supported by a user agent, they should be treated like unrecognized values per the CSS forward compatibility parsing rules ([CSS21], Chapter 4). RGBA values must not be treated as simply an RGB value with the opacity ignored.

4.2.3. ‘transparent’ color keyword

CSS1 introduced the ‘transparent’ value for the background-color property. CSS2 allowed border-color to also accept the ‘transparent’ value. The Open eBook(tm) Publication Structure 1.0.1 [OEB101] extended the ‘color’ property to also accept the ‘transparent’ keyword. CSS3 extends the color value to include the ‘transparent’ keyword to allow its use with all properties that accept a value. This simplifies the definition of those properties in CSS3.

transparent

Fully transparent. This keyword can be considered a shorthand for transparent black, rgba(0,0,0,0), which is its computed value.

4.2.4. HSL color values

CSS3 adds numerical hue-saturation-lightness (HSL) colors as a complement to numerical RGB colors. It has been observed that RGB colors have the following limitations:

There are several other color schemes possible. Some advantages of HSL are that it is symmetrical to lightness and darkness (which is not the case with HSV for example), and it is trivial to convert HSL to RGB.

HSL colors are encoding as a triple (hue, saturation, lightness). Hue is represented as an angle of the color circle (i.e. the rainbow represented in a circle). This angle is so typically measured in degrees that the unit is implicit in CSS; syntactically, only a is given. By definition red=0=360, and the other colors are spread around the circle, so green=120, blue=240, etc. As an angle, it implicitly wraps around such that -120=240 and 480=120. One way an implementation could normalize such an angle x to the range [0,360) (i.e. zero degrees, inclusive, to 360 degrees, exclusive) is to compute (((x mod 360) + 360) mod 360). Saturation and lightness are represented as percentages. 100% is full saturation, and 0% is a shade of gray. 0% lightness is black, 100% lightness is white, and 50% lightness is “normal”.

So for instance:

Example(s):

The advantage of HSL over RGB is that it is far more intuitive: you can guess at the colors you want, and then tweak. It is also easier to create sets of matching colors (by keeping the hue the same and varying the lightness/darkness, and saturation)

If saturation is less than 0%, implementations must clip it to 0%. If the resulting value is outside the device gamut, implementations must clip it to the device gamut. This clipping should preserve the hue when possible, but is otherwise undefined. (In other words, the clipping is different from applying the rules for clipping of RGB colors after applying the algorithm below for converting HSL to RGB.)

Converting an HSL color to sRGB is straightforward mathematically. Here's a sample implementation of the conversion algorithm in JavaScript. It returns an array of three numbers representing the red, green, and blue channels of the colors, normalized to the range [0, 1].

function hslToRgb (hue, sat, light) {
  hue = hue % 360;

  if (hue < 0) {
      hue += 360;
  }

  sat /= 100;
  light /= 100;

  function f(n) {
      let k = (n + hue/30) % 12;
      let a = sat * Math.min(light, 1 - light);
      return light - a * Math.max(-1, Math.min(k - 3, 9 - k, 1));
  }

  return [f(0), f(8), f(4)];

}

4.2.4.1. HSL examples

Each table below represents one hue. Twelve equally spaced colors (i.e. at 30° intervals) have been chosen from the color circle: red, yellow, green, cyan, blue, magenta, with all the intermediate colors (the last is the color between magenta and red).

In each table, the X axis represents the saturation while the Y axis represents the lightness.

0° Reds
100% 80% 60% 40% 20% 0%
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
30° Reds-Yellows (=Oranges)
100% 80% 60% 40% 20% 0%
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
60° Yellows
100% 80% 60% 40% 20% 0%
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
90° Yellow-Greens
100% 80% 60% 40% 20% 0%
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
120° Greens
100% 80% 60% 40% 20% 0%
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
150° Green-Cyans
100% 80% 60% 40% 20% 0%
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
180° Cyans
100% 80% 60% 40% 20% 0%
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
210° Cyan-Blues
100% 80% 60% 40% 20% 0%
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
240° blues
100% 80% 60% 40% 20% 0%
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
270° Blue-Magentas
100% 80% 60% 40% 20% 0%
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
300° Magentas
100% 80% 60% 40% 20% 0%
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
330° Magenta-Reds
100% 80% 60% 40% 20% 0%
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%

4.2.5.HSLA color values

Just as the ‘rgb()’ functional notation has the ‘rgba()’ alpha counterpart, the ‘hsl()’ functional notation has the ‘hsla()’ alpha counterpart. See simple alpha compositing for details. These examples specify the same color:

Example(s):

em { color: hsl(120, 100%, 50%) } /* green / em { color: hsla(120, 100%, 50%, 1) } / the same, with explicit opacity of 1 */

The format of an HSLA color value in the functional notation is ‘hsla(’ followed by the hue in degrees, saturation and lightness as a percentage, and an , followed by ‘)’. White space characters are allowed around the numerical values.

Implementations must clip the hue, saturation, and lightness components of HSLA color values to the device gamut according to the rules for the HSL color value composed of those components.

These examples specify effects that are possible with the hsla() notation:

Example(s):

p { color: hsla(240, 100%, 50%, 0.5) } /* semi-transparent solid blue / p { color: hsla(30, 100%, 50%, 0.1) } / very transparent solid orange */

4.3. Extended color keywords

The table below provides a list of the X11 colors [X11COLORS] supported by popular browsers with the addition of gray/grey variants from SVG 1.0. The resulting list is precisely the same as the SVG 1.0 color keyword names. This specification extends their definition beyond SVG. The two color swatches on the left illustrate setting the background color of a table cell in two ways: The first column uses the named color value, and the second column uses the respective numeric color value.

Named Numeric Color name Hex rgb Decimal
aliceblue #f0f8ff 240,248,255
antiquewhite #faebd7 250,235,215
aqua #00ffff 0,255,255
aquamarine #7fffd4 127,255,212
azure #f0ffff 240,255,255
beige #f5f5dc 245,245,220
bisque #ffe4c4 255,228,196
black #000000 0,0,0
blanchedalmond #ffebcd 255,235,205
blue #0000ff 0,0,255
blueviolet #8a2be2 138,43,226
brown #a52a2a 165,42,42
burlywood #deb887 222,184,135
cadetblue #5f9ea0 95,158,160
chartreuse #7fff00 127,255,0
chocolate #d2691e 210,105,30
coral #ff7f50 255,127,80
cornflowerblue #6495ed 100,149,237
cornsilk #fff8dc 255,248,220
crimson #dc143c 220,20,60
cyan #00ffff 0,255,255
darkblue #00008b 0,0,139
darkcyan #008b8b 0,139,139
darkgoldenrod #b8860b 184,134,11
darkgray #a9a9a9 169,169,169
darkgreen #006400 0,100,0
darkgrey #a9a9a9 169,169,169
darkkhaki #bdb76b 189,183,107
darkmagenta #8b008b 139,0,139
darkolivegreen #556b2f 85,107,47
darkorange #ff8c00 255,140,0
darkorchid #9932cc 153,50,204
darkred #8b0000 139,0,0
darksalmon #e9967a 233,150,122
darkseagreen #8fbc8f 143,188,143
darkslateblue #483d8b 72,61,139
darkslategray #2f4f4f 47,79,79
darkslategrey #2f4f4f 47,79,79
darkturquoise #00ced1 0,206,209
darkviolet #9400d3 148,0,211
deeppink #ff1493 255,20,147
deepskyblue #00bfff 0,191,255
dimgray #696969 105,105,105
dimgrey #696969 105,105,105
dodgerblue #1e90ff 30,144,255
firebrick #b22222 178,34,34
floralwhite #fffaf0 255,250,240
forestgreen #228b22 34,139,34
fuchsia #ff00ff 255,0,255
gainsboro #dcdcdc 220,220,220
ghostwhite #f8f8ff 248,248,255
gold #ffd700 255,215,0
goldenrod #daa520 218,165,32
gray #808080 128,128,128
green #008000 0,128,0
greenyellow #adff2f 173,255,47
grey #808080 128,128,128
honeydew #f0fff0 240,255,240
hotpink #ff69b4 255,105,180
indianred #cd5c5c 205,92,92
indigo #4b0082 75,0,130
ivory #fffff0 255,255,240
khaki #f0e68c 240,230,140
lavender #e6e6fa 230,230,250
lavenderblush #fff0f5 255,240,245
lawngreen #7cfc00 124,252,0
lemonchiffon #fffacd 255,250,205
lightblue #add8e6 173,216,230
lightcoral #f08080 240,128,128
lightcyan #e0ffff 224,255,255
lightgoldenrodyellow #fafad2 250,250,210
lightgray #d3d3d3 211,211,211
lightgreen #90ee90 144,238,144
lightgrey #d3d3d3 211,211,211
lightpink #ffb6c1 255,182,193
lightsalmon #ffa07a 255,160,122
lightseagreen #20b2aa 32,178,170
lightskyblue #87cefa 135,206,250
lightslategray #778899 119,136,153
lightslategrey #778899 119,136,153
lightsteelblue #b0c4de 176,196,222
lightyellow #ffffe0 255,255,224
lime #00ff00 0,255,0
limegreen #32cd32 50,205,50
linen #faf0e6 250,240,230
magenta #ff00ff 255,0,255
maroon #800000 128,0,0
mediumaquamarine #66cdaa 102,205,170
mediumblue #0000cd 0,0,205
mediumorchid #ba55d3 186,85,211
mediumpurple #9370db 147,112,219
mediumseagreen #3cb371 60,179,113
mediumslateblue #7b68ee 123,104,238
mediumspringgreen #00fa9a 0,250,154
mediumturquoise #48d1cc 72,209,204
mediumvioletred #c71585 199,21,133
midnightblue #191970 25,25,112
mintcream #f5fffa 245,255,250
mistyrose #ffe4e1 255,228,225
moccasin #ffe4b5 255,228,181
navajowhite #ffdead 255,222,173
navy #000080 0,0,128
oldlace #fdf5e6 253,245,230
olive #808000 128,128,0
olivedrab #6b8e23 107,142,35
orange #ffa500 255,165,0
orangered #ff4500 255,69,0
orchid #da70d6 218,112,214
palegoldenrod #eee8aa 238,232,170
palegreen #98fb98 152,251,152
paleturquoise #afeeee 175,238,238
palevioletred #db7093 219,112,147
papayawhip #ffefd5 255,239,213
peachpuff #ffdab9 255,218,185
peru #cd853f 205,133,63
pink #ffc0cb 255,192,203
plum #dda0dd 221,160,221
powderblue #b0e0e6 176,224,230
purple #800080 128,0,128
red #ff0000 255,0,0
rosybrown #bc8f8f 188,143,143
royalblue #4169e1 65,105,225
saddlebrown #8b4513 139,69,19
salmon #fa8072 250,128,114
sandybrown #f4a460 244,164,96
seagreen #2e8b57 46,139,87
seashell #fff5ee 255,245,238
sienna #a0522d 160,82,45
silver #c0c0c0 192,192,192
skyblue #87ceeb 135,206,235
slateblue #6a5acd 106,90,205
slategray #708090 112,128,144
slategrey #708090 112,128,144
snow #fffafa 255,250,250
springgreen #00ff7f 0,255,127
steelblue #4682b4 70,130,180
tan #d2b48c 210,180,140
teal #008080 0,128,128
thistle #d8bfd8 216,191,216
tomato #ff6347 255,99,71
turquoise #40e0d0 64,224,208
violet #ee82ee 238,130,238
wheat #f5deb3 245,222,179
white #ffffff 255,255,255
whitesmoke #f5f5f5 245,245,245
yellow #ffff00 255,255,0
yellowgreen #9acd32 154,205,50

4.4. ‘currentColor’ color keyword

CSS1 and CSS2 defined the initial value of the ‘border-color’ property to be the value of the ‘color’ property but did not define a corresponding keyword. This omission was recognized by SVG, and thus SVG 1.0 introduced the ‘currentColor’ value for the ‘fill’, ‘stroke’, ‘stop-color’, ‘flood-color’, and ‘lighting-color’ properties. CSS3 extends the color value to include the ‘currentColor’ keyword to allow its use with all properties that accept a value. This simplifies the definition of those properties in CSS3.

currentColor

The value of the ‘color’ property. The used value of the ‘currentColor’ keyword is the computed value of the ‘color’ property. If the ‘currentColor’ keyword is set on the ‘color’ property itself, it is treated as ‘color: inherit’.

4.5. CSS system colors

4.5.1. CSS2 system colors

Deprecated. In addition to being able to assign color keyword values to text, backgrounds, etc., CSS2 allowed authors to specify colors in a manner that integrated them into the user's graphic environment.

For systems that do not have a corresponding value, the specified value should be mapped to the nearest system color value, or to a default color. Note that some profiles of CSS may not support System Colors at all.

The following lists additional values for color-related CSS values and their general meaning. Any color property can take one of the following names. Although these are ASCII case-insensitive, it is recommended that the mixed capitalization shown below be used, to make the names more legible.

ActiveBorder

Active window border.

ActiveCaption

Active window caption.

AppWorkspace

Background color of multiple document interface.

Background

Desktop background.

ButtonFace

The face background color for 3-D elements that appear 3-D due to one layer of surrounding border.

ButtonHighlight

The color of the border facing the light source for 3-D elements that appear 3-D due to one layer of surrounding border.

ButtonShadow

The color of the border away from the light source for 3-D elements that appear 3-D due to one layer of surrounding border.

ButtonText

Text on push buttons.

CaptionText

Text in caption, size box, and scrollbar arrow box.

GrayText

Grayed (disabled) text. This color is set to #000 if the current display driver does not support a solid gray color.

Highlight

Item(s) selected in a control.

HighlightText

Text of item(s) selected in a control.

InactiveBorder

Inactive window border.

InactiveCaption

Inactive window caption.

InactiveCaptionText

Color of text in an inactive caption.

InfoBackground

Background color for tooltip controls.

InfoText

Text color for tooltip controls.

Menu background.

Text in menus.

Scrollbar

Scroll bar gray area.

ThreeDDarkShadow

The color of the darker (generally outer) of the two borders away from the light source for 3-D elements that appear 3-D due to two concentric layers of surrounding border.

ThreeDFace

The face background color for 3-D elements that appear 3-D due to two concentric layers of surrounding border.

ThreeDHighlight

The color of the lighter (generally outer) of the two borders facing the light source for 3-D elements that appear 3-D due to two concentric layers of surrounding border.

ThreeDLightShadow

The color of the darker (generally inner) of the two borders facing the light source for 3-D elements that appear 3-D due to two concentric layers of surrounding border.

ThreeDShadow

The color of the lighter (generally inner) of the two borders away from the light source for 3-D elements that appear 3-D due to two concentric layers of surrounding border.

Window

Window background.

WindowFrame

Window frame.

WindowText

Text in windows.

DEPRECATED EXAMPLE(S):

For example, to set the foreground and background colors of a paragraph to the same foreground and background colors of the user's window, write the following:

p { color: WindowText; background-color: Window }

4.6. Notes on using colors

Although colors can add significant amounts of information to document and make them more readable, please consider the W3C Web Content Accessibility Guidelines [WCAG20] when including color in your documents.

5. Simple alpha compositing

When drawing, implementations must handle alpha according to the rules in Section 14.2 Simple alpha compositing of [SVG11]. (If the ‘color-interpolation’ or ‘color-rendering’ properties mentioned in that section are not implemented or do not apply, implementations must act as though they have their initial values.)

6. Sample style sheet for (X)HTML

This appendix is informative, not normative. This style sheet could be used by an implementation as part of its default styling of HTML4, XHTML1, XHTML1.1, XHTML Basic, and other XHTML Family documents.

html { color: black; background: white; }

/* traditional desktop user agent colors for hyperlinks */ :link { color: blue; } :visited { color: purple; }

/* default focus outline / :focus { outline: 1px dotted; / or 1px dotted invert */ }

7. Profiles

Each specification using CSS3 Color must define the subset of CSS3 Color features it allows and excludes, and describe the local meaning of all the components of that subset.

Non normative examples:

CSS3 Color profile
Specification HTML4
Accepts Basic color keywords RGB six digit hex color values
Excludes ‘color’ property ‘opacity’ property RGB three digit hex color values and RGB functional notation color value RGBA color values HSL and HSLA color values Extended color keywords ‘currentColor’ color value CSS2 UI Colors ‘transparent’ color value
Extra constraints none.
CSS3 Color profile
Specification CSS level 1
Accepts ‘color’ property Basic color keywords RGB color values
Excludes ‘opacity’ property RGBA color values HSL and HSLA color values Extended color keywords ‘currentColor’ color value CSS2 UI Colors ‘transparent’ color value
Extra constraints none.
CSS3 Color profile
Specification CSS level 2
Accepts ‘color’ property Basic color keywords RGB color values CSS2 UI Colors ‘transparent’ color value
Excludes ‘opacity’ property RGBA color values HSL and HSLA color values Extended color keywords ‘currentColor’ color value
Extra constraints ‘transparent’ color value not valid for ‘color’ property. ‘orange’ color value (part of Extended color keywords) is accepted in CSS level 2 revision 1
CSS3 Color profile
Specification SVG 1.0 and 1.1
Accepts ‘color’ property ‘opacity’ property Basic color keywords RGB color values CSS2 UI Colors Extended color keywords ‘currentColor’ color value
Excludes RGBA color values HSL and HSLA color values ‘transparent’ color value
Extra constraints ‘currentColor’ color value not valid for ‘color’ property.

8. Test suite

A CSS Color Module Test Suite has been developed, although further tests may be added. This test suite is intended to allow user agents to verify their basic conformance to the specification. This test suite does not pretend to be exhaustive and does not cover all possible numerical color values. These tests are available at https://test.csswg.org/harness/suite/css-color-3_dev/.

9. Future features

This section is non-normative.

A number of features related to color management, such as the ‘@color-profile’ at-rule for specifying ICC profiles, a means to control the rendering intent of those profiles, and a way to use those profiles (the ‘color-profile’ property) were removed from CSS Color 3 due to lack of implementation interest at the time.

Development of related features continued in CSS Color 4 and 5; see the ‘color()’ function, the ‘@color-profile’ at-rule, and the ‘rendering-intent’ descriptor.

10. Acknowledgments

Thanks to Brad Pettit both for writing up color-profiles, and for implementing it. Thanks to Steven Pemberton for a write up on HSL colors. Thanks especially to the feedback from Marc Attinasi, Bert Bos, Joe Clark, fantasai, Patrick Garies, Tony Graham, Ian Hickson, Susan Lesch, Alex LeDonne, Cameron McCormack, Krzysztof Maczyński, Chris Moschini, Chris Murphy, Christoph Päper, David Perrell, Jacob Refstrup, Dave Singer, Jonathan Stanley, Andrew Thompson, Russ Weakley, Etan Wexler, David Woolley, Boris Zbarsky, Steve Zilles, the XSL FO subgroup of the XSL working group, and all the rest of the www-style community. And thanks to Chris Lilley for being the resident CSS Color expert.

11. Changes

Changes since the05 August 2021 Recommendation

The following editorial corrections were made:

Changes since the19 June 2018 Recommendation

Changes since the 5 December 2017 Candidate Recommendation

Changes since the 2011 June 07 Recommendation

This document differs from the 2011 June 07 Recommendation in that it contains the following changes:

For changes in earlier drafts, seechanges in previous Recommendation and previous versions linked therefrom.

Prior dispositions of comments:

12. References

12.1. Normative

[COLORIMETRY]

Colorimetry, Third Edition. CIE 15:2004. ISBN 978-3-901906-33-6

[CSS21]

Bert Bos; et al. Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification. 7 June 2011. W3C Recommendation. URL: http://www.w3.org/TR/2011/REC-CSS2-20110607

[SRGB]

Multimedia systems and equipment - Colour measurement and management - Part 2-1: Colour management - Default RGB colour space - sRGB. IEC 61966-2-1 (1999-10) ISBN: 2-8318-4989-6 - ICS codes: 33.160.60, 37.080 - TC 100 - 51 pp. as amended by Amendment A1:2003. URL: https://webstore.iec.ch/publication/6168

[SVG11]

Erik Dahlström; et al. Scalable Vector Graphics (SVG) 1.1 (Second Edition). 16 August 2011. W3C Recommendation. URL: http://www.w3.org/TR/2011/REC-SVG11-20110816/

12.2. Informative

[CSS-UI-3]

Tantek Çelik; Florian Rivoal. CSS Basic User Interface Module Level 3 (CSS3 UI). 21 June 2018. W3C Recommendation. URL: https://www.w3.org/TR/2018/REC-css-ui-3-20180621/

[CSS2]

Bert Bos; et al. Cascading Style Sheets, level 2 (CSS2) Specification. 07 June 2011. W3C Recommendation. URL: http://www.w3.org/TR/2011/REC-CSS2-20110607

[HTML401]

Dave Raggett; Arnaud Le Hors; Ian Jacobs. HTML 4.01 Specification. 24 December 1999. W3C Recommendation. URL: http://www.w3.org/TR/1999/REC-html401-19991224

[OEB101]

Open eBook(tm) Publication Structure 1.0.1. Open eBook Forum(tm). 02 July 2001. URL: https://www.loc.gov/preservation/digital/formats/fdd/fdd000054.shtml

[SVG10]

Jon Ferraiolo. Scalable Vector Graphics (SVG) 1.0 Specification. 4 September 2001. W3C Recommendation. URL: http://www.w3.org/TR/2001/REC-SVG-20010904

[WCAG20]

Ben Caldwell; et al. Web Content Accessibility Guidelines (WCAG) 2.0. 11 December 2008. W3C Recommendation. URL: http://www.w3.org/TR/2008/REC-WCAG20-20081211/

[X11COLORS]

Wikipedia X11 color names. URL: https://en.wikipedia.org/wiki/X11_color_names

[XML10]

C. M. Sperberg-McQueen; et al. Extensible Markup Language (XML) 1.0 (Fifth Edition). 26 November 2008. W3C Recommendation. URL: http://www.w3.org/TR/2008/REC-xml-20081126/

Index

Property index

Property Values Initial Applies to Inh. Percentages
color | inherit depends on user agent yes N/A
opacity | inherit 1 no N/A