Web colors

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Web colors are colors used in displaying web pages, and the methods for describing and specifying those colors. Colors may be specified as an RGB triplet or in hexadecimal format (a hex triplet). They may also be specified according to their common English names in some cases. Often a color tool or other graphics software is used to generate color values. In some uses, hexadecimal color codes are specified with notation using a leading number sign (#).[1][2] A color is specified according to the intensity of its red, green and blue components, each represented by eight bits. Thus, there are 24 bits used to specify a web color, and 16,777,216 colors that may be so specified.

The first versions of Mosaic and Netscape Navigator used the X11 color names as the basis for their color lists, as both started as X Window System applications.[3]

Web colors have an unambiguous colorimetric definition, sRGB, which relates the chromaticities of a particular phosphor set, a given transfer curve, adaptive whitepoint, and viewing conditions.[4] These have been chosen to be similar to many real-world monitors and viewing conditions, so that even without color management rendering is fairly close to the specified values. However, user agents vary in the fidelity with which they represent the specified colors. More advanced user agents use color management to provide better color fidelity; this is particularly important for Web-to-print applications.

Hex triplet[edit]

A hex triplet is a six-digit, three-byte hexadecimal number used in HTML, CSS, SVG, and other computing applications, to represent colors. The bytes represent the red, green and blue components of the color. One byte represents a number in the range 00 to FF (in hexadecimal notation), or 0 to 255 in decimal notation. This represents the least (0) to the most (255) intensity of each of the color components. Thus web colors specify colors in the Truecolor (24-bit RGB) color scheme. The hex triplet is formed by concatenating three bytes in hexadecimal notation, in the following order:

Byte 1: red value (color type red)
Byte 2: green value (color type green)
Byte 3: blue value (color type blue)

For example, consider the color where the red/green/blue values are decimal numbers: red=36, green=104, blue=160 (a greyish-blue color). The decimal numbers 36, 104 and 160 are equivalent to the hexadecimal numbers 24, 68 and A0 respectively. The hex triplet is obtained by concatenating the 6 hexadecimal digits together, 2468A0 in this example.

Note that if any one of the three color values is less than 16 (decimal) or 10 (hex), it must be represented with a leading zero so that the triplet always has exactly six digits. For example, the decimal triplet 4, 8, 16 would be represented by the hex digits 04, 08, 10, forming the hex triplet 040810.

The number of colors that can be represented by this system is 2563 or 224 = 16,777,216.

Shorthand hexadecimal form[edit]

An abbreviated, three (hexadecimal) digits form is sometimes used.[5] Expanding this form to the six-digit form is as simple as doubling each digit: 09C becomes 0099CC as presented on the following CSS example:

.threedigit { color: #09C;    }
.sixdigit   { color: #0099CC; } /*same color as above*/

The three-digit form is described in the CSS specification, not in HTML. As a result, the three-digit form in an attribute other than "style" is not interpreted as a valid color in some browsers.

This shorthand form reduces the palette to 4,096 colors, equivalent of 12-bit color as opposed to 24-bit color using the whole six-digit form (16,777,216 colors). However, this limitation is often sufficient for text based documents.

Converting RGB to hexadecimal[edit]

RGB values are usually given in the 0–255 range; if they are in the 0–1 range, the values are multiplied by 255 before conversion. This number divided by 16 (integer division; ignoring any remainder) gives us the first hexadecimal digit (between 0 and F, where the letters A to F represent the numbers 10 to 15. See hexadecimal for more details). The remainder gives us the second hexadecimal digit. For instance the RGB value 201 divides into 12 groups of 16, thus the first digit is C. A remainder of 9 gives us the hexadecimal number C9. This process is repeated for each of the three color values.

Conversion between number bases is a common feature of calculators, including both hand-held models and the software calculators bundled with most modern operating systems. Web-based tools specifically for converting color values are also available.

HTML color names[edit]

The HTML 4.01 specification[6] defines 16 named colors, as follows (names are defined in this context to be case-insensitive):

CSS 1–2.0 / HTML 3.2–4 / VGA color names
Name Hex (RGB) Red
(RGB)
Green
(RGB)
Blue
(RGB)
Hue
(HSL/HSV)
Satur
(HSL)
Light
(HSL)
Satur
(HSV)
Value
(HSV)
CGA number (name); alias
White #FFFFFF 100% 100% 100% 0% 100% 0% 100% 15 (white)
Silver #C0C0C0 75% 75% 75% 0% 75% 0% 75% 07 (light gray)
Gray #808080 50% 50% 50% 0% 50% 0% 50% 08 (dark gray)
Black #000000 0% 0% 0% 0% 0% 0% 0% 00 (black)
Red #FF0000 100% 0% 0% 100% 50% 100% 100% 12 (high red)
Maroon #800000 50% 0% 0% 100% 25% 100% 50% 04 (low red)
Yellow #FFFF00 100% 100% 0% 60° 100% 50% 100% 100% 14 (yellow)
Olive #808000 50% 50% 0% 60° 100% 25% 100% 50% 06 (brown)
Lime #00FF00 0% 100% 0% 120° 100% 50% 100% 100% 10 (high green); green
Green #008000 0% 50% 0% 120° 100% 25% 100% 50% 02 (low green)
Aqua #00FFFF 0% 100% 100% 180° 100% 50% 100% 100% 11 (high cyan); cyan
Teal #008080 0% 50% 50% 180° 100% 25% 100% 50% 03 (low cyan)
Blue #0000FF 0% 0% 100% 240° 100% 50% 100% 100% 09 (high blue)
Navy #000080 0% 0% 50% 240° 100% 25% 100% 50% 01 (low blue)
Fuchsia #FF00FF 100% 0% 100% 300° 100% 50% 100% 100% 13 (high magenta); magenta
Purple #800080 50% 0% 50% 300° 100% 25% 100% 50% 05 (low magenta)

These 16 were labelled as sRGB and included in the HTML 3.0 specification, which noted they were "the standard 16 colors supported with the Windows VGA palette."[7]

X11 color names[edit]

Main article: X11 color names

In addition, a number of colors are defined by web browsers. A particular browser may not recognize all of these colors, but as of 2005 all modern general-use browsers support the full list of colors. Many of these colors are from the list of X11 color names distributed with the X Window System. These colors were standardized by SVG 1.0, and are accepted by SVG Full user agents. They are not part of SVG Tiny.

The list of colors actually shipped with the X11 product varies between implementations, and clashes with certain of the HTML names such as green. Furthermore, X11 colors are defined as simple RGB (hence, no particular color space), rather than sRGB. This means that the list of colors found in X11 (e.g. in /usr/lib/X11/rgb.txt) should not directly be used to choose colors for the web.[8]

The list of web "X11 colors" from the CSS3 specification, along with their hexadecimal and decimal equivalents, is shown below, compare the alphabetical lists in the W3C standards. Note that this includes the common synonyms: aqua (HTML4/CSS 1.0 standard name) and cyan (common sRGB name), magenta (common sRGB name) and fuchsia (HTML4/CSS 1.0 standard name), gray (HTML4/CSS 1.0 standard name) and grey.[9][10]

HTML name Hex code
R   G   B
Decimal code
R   G   B
Pink colors
Pink FF C0 CB 255 192 203
LightPink FF B6 C1 255 182 193
HotPink FF 69 B4 255 105 180
DeepPink FF 14 93 255  20 147
PaleVioletRed DB 70 93 219 112 147
MediumVioletRed C7 15 85 199  21 133
Red colors
LightSalmon FF A0 7A 255 160 122
Salmon FA 80 72 250 128 114
DarkSalmon E9 96 7A 233 150 122
LightCoral F0 80 80 240 128 128
IndianRed CD 5C 5C 205  92  92
Crimson DC 14 3C 220  20  60
FireBrick B2 22 22 178  34  34
DarkRed 8B 00 00 139   0   0
Red FF 00 00 255   0   0
Orange colors
OrangeRed FF 45 00 255  69   0
Tomato FF 63 47 255  99  71
Coral FF 7F 50 255 127  80
DarkOrange FF 8C 00 255 140   0
Orange FF A5 00 255 165   0
Yellow colors
Yellow FF FF 00 255 255   0
LightYellow FF FF E0 255 255 224
LemonChiffon FF FA CD 255 250 205
LightGoldenrodYellow FA FA D2 250 250 210
PapayaWhip FF EF D5 255 239 213
Moccasin FF E4 B5 255 228 181
PeachPuff FF DA B9 255 218 185
PaleGoldenrod EE E8 AA 238 232 170
Khaki F0 E6 8C 240 230 140
DarkKhaki BD B7 6B 189 183 107
Gold FF D7 00 255 215   0
Brown colors
Cornsilk FF F8 DC 255 248 220
BlanchedAlmond FF EB CD 255 235 205
Bisque FF E4 C4 255 228 196
NavajoWhite FF DE AD 255 222 173
Wheat F5 DE B3 245 222 179
BurlyWood DE B8 87 222 184 135
Tan D2 B4 8C 210 180 140
RosyBrown BC 8F 8F 188 143 143
SandyBrown F4 A4 60 244 164  96
Goldenrod DA A5 20 218 165  32
DarkGoldenrod B8 86 0B 184 134  11
Peru CD 85 3F 205 133  63
Chocolate D2 69 1E 210 105  30
SaddleBrown 8B 45 13 139  69  19
Sienna A0 52 2D 160  82  45
Brown A5 2A 2A 165  42  42
Maroon 80 00 00 128   0   0
HTML name Hex code
R   G   B
Decimal code
R   G   B
Green colors
DarkOliveGreen 55 6B 2F  85 107  47
Olive 80 80 00 128 128   0
OliveDrab 6B 8E 23 107 142  35
YellowGreen 9A CD 32 154 205  50
LimeGreen 32 CD 32  50 205  50
Lime 00 FF 00   0 255   0
LawnGreen 7C FC 00 124 252   0
Chartreuse 7F FF 00 127 255   0
GreenYellow AD FF 2F 173 255  47
SpringGreen 00 FF 7F   0 255 127
MediumSpringGreen 00 FA 9A   0 250 154
LightGreen 90 EE 90 144 238 144
PaleGreen 98 FB 98 152 251 152
DarkSeaGreen 8F BC 8F 143 188 143
MediumSeaGreen 3C B3 71  60 179 113
SeaGreen 2E 8B 57  46 139  87
ForestGreen 22 8B 22  34 139  34
Green 00 80 00   0 128   0
DarkGreen 00 64 00   0 100   0
Cyan colors
MediumAquamarine 66 CD AA 102 205 170
Aqua 00 FF FF   0 255 255
Cyan 00 FF FF   0 255 255
LightCyan E0 FF FF 224 255 255
PaleTurquoise AF EE EE 175 238 238
Aquamarine 7F FF D4 127 255 212
Turquoise 40 E0 D0  64 224 208
MediumTurquoise 48 D1 CC  72 209 204
DarkTurquoise 00 CE D1   0 206 209
LightSeaGreen 20 B2 AA  32 178 170
CadetBlue 5F 9E A0  95 158 160
DarkCyan 00 8B 8B   0 139 139
Teal 00 80 80   0 128 128
Blue colors
LightSteelBlue B0 C4 DE 176 196 222
PowderBlue B0 E0 E6 176 224 230
LightBlue AD D8 E6 173 216 230
SkyBlue 87 CE EB 135 206 235
LightSkyBlue 87 CE FA 135 206 250
DeepSkyBlue 00 BF FF   0 191 255
DodgerBlue 1E 90 FF  30 144 255
CornflowerBlue 64 95 ED 100 149 237
SteelBlue 46 82 B4  70 130 180
RoyalBlue 41 69 E1  65 105 225
Blue 00 00 FF   0   0 255
MediumBlue 00 00 CD   0   0 205
DarkBlue 00 00 8B   0   0 139
Navy 00 00 80   0   0 128
MidnightBlue 19 19 70  25  25 112
HTML name Hex code
R   G   B
Decimal code
R   G   B
Purple colors
Lavender E6 E6 FA 230 230 250
Thistle D8 BF D8 216 191 216
Plum DD A0 DD 221 160 221
Violet EE 82 EE 238 130 238
Orchid DA 70 D6 218 112 214
Fuchsia FF 00 FF 255   0 255
Magenta FF 00 FF 255   0 255
MediumOrchid BA 55 D3 186  85 211
MediumPurple 93 70 DB 147 112 219
BlueViolet 8A 2B E2 138  43 226
DarkViolet 94 00 D3 148   0 211
DarkOrchid 99 32 CC 153  50 204
DarkMagenta 8B 00 8B 139   0 139
Purple 80 00 80 128   0 128
Indigo 4B 00 82  75   0 130
DarkSlateBlue 48 3D 8B  72  61 139
SlateBlue 6A 5A CD 106  90 205
MediumSlateBlue 7B 68 EE 123 104 238
White colors
White FF FF FF 255 255 255
Snow FF FA FA 255 250 250
Honeydew F0 FF F0 240 255 240
MintCream F5 FF FA 245 255 250
Azure F0 FF FF 240 255 255
AliceBlue F0 F8 FF 240 248 255
GhostWhite F8 F8 FF 248 248 255
WhiteSmoke F5 F5 F5 245 245 245
Seashell FF F5 EE 255 245 238
Beige F5 F5 DC 245 245 220
OldLace FD F5 E6 253 245 230
FloralWhite FF FA F0 255 250 240
Ivory FF FF F0 255 255 240
AntiqueWhite FA EB D7 250 235 215
Linen FA F0 E6 250 240 230
LavenderBlush FF F0 F5 255 240 245
MistyRose FF E4 E1 255 228 225
Gray/Black colors
Gainsboro DC DC DC 220 220 220
LightGrey D3 D3 D3 211 211 211
Silver C0 C0 C0 192 192 192
DarkGray A9 A9 A9 169 169 169
Gray 80 80 80 128 128 128
DimGray 69 69 69 105 105 105
LightSlateGray 77 88 99 119 136 153
SlateGray 70 80 90 112 128 144
DarkSlateGray 2F 4F 4F  47  79  79
Black 00 00 00   0   0   0

Web-safe colors[edit]

At one time many computer displays were only capable of displaying 256 colors. These may be dictated by the hardware or changeable by a "color table". When a color is found (e.g., in an image) that is not one available, a different one has to be used. This can be done by either using the closest color, which greatly speeds up the load time, or by using dithering, which results in more accurate results, but takes longer to load due to the complex calculations.

There were various attempts to make a "standard" color palette. A set of colors was needed that could be shown without dithering on 256-color displays; the number 216 was chosen partly because computer operating systems customarily reserved sixteen to twenty colors for their own use; it was also selected because it allows exactly six equally-spaced shades of red, green, and blue (6 × 6 × 6 = 216), each from 00 to FF (including both limits).

The list of colors is often presented as if it has special properties that render them immune to dithering. In fact, on 256-color displays applications can set a palette of any selection of colors that they choose, dithering the rest. These colors were chosen specifically because they matched the palettes selected by the then leading browser applications. There were not radically different palettes in use in different popular browsers.[citation needed]

"Web-safe" colors had a flaw in that, on systems such as X11 where the palette is shared between applications, smaller color cubes (5×5×5 or 4×4×4) were often allocated by browsers—thus, the "web safe" colors would actually dither on such systems. Better results were obtained by providing an image with a larger range of colors and allowing the browser to quantize the color space if needed, rather than suffer the quality loss of a double quantization.

As of 2011, personal computers typically[11] have 24-bit (TrueColor) and the use of "web-safe" colors has fallen into practical disuse. Even mobile devices have at least 16-bit color; this could be attributed to the inclusion of cameras on cellphones, for better viewing of the photos taken by such devices.[citation needed]

The "web-safe" colors do not all have standard names, but each can be specified by an RGB triplet: each component (red, green, and blue) takes one of the six values from the following table (out of the 256 possible values available for each component in full 24-bit color).

6 shades of each color
Key Hex Decimal Fraction
0 00 0 0
3 33 51 0.2
6 66 102 0.4
9 99 153 0.6
C or (12) CC 204 0.8
F or (15) FF 255 1

The following table shows all of the "web-safe" colors. (One shortcoming of the web-safe palette is its poor selection of light background colors.) The intensities at the low end of the range, especially the two darkest, are often hard to distinguish.

Color table[edit]

In the table below, each color code listed is a shorthand for the RGB value; for example, code 609 is equivalent to RGB code 102-0-153 or HEX code #660099.

Web-Safe Colors
*000* 300 600 900 C00 *F00*
*003* 303 603 903 C03 *F03*
006 306 606 906 C06 F06
009 309 609 909 C09 F09
00C 30C 60C 90C C0C F0C
*00F* 30F 60F 90F C0F *F0F*
030 330 630 930 C30 F30
033 333 633 933 C33 F33
036 336 636 936 C36 F36
039 339 639 939 C39 F39
03C 33C 63C 93C C3C F3C
03F 33F 63F 93F C3F F3F
060 360 660 960 C60 F60
063 363 663 963 C63 F63
066 366 666 966 C66 F66
069 369 669 969 C69 F69
06C 36C 66C 96C C6C F6C
06F 36F 66F 96F C6F F6F
090 390 690 990 C90 F90
093 393 693 993 C93 F93
096 396 696 996 C96 F96
099 399 699 999 C99 F99
09C 39C 69C 99C C9C F9C
09F 39F 69F 99F C9F F9F
0C0 3C0 6C0 9C0 CC0 FC0
0C3 3C3 6C3 9C3 CC3 FC3
0C6 3C6 6C6 9C6 CC6 FC6
0C9 3C9 6C9 9C9 CC9 FC9
0CC 3CC 6CC 9CC CCC FCC
0CF 3CF 6CF 9CF CCF FCF
*0F0* 3F0 *6F0* 9F0 CF0 *FF0*
0F3 *3F3* *6F3* 9F3 CF3 *FF3*
*0F6* *3F6* 6F6 9F6 *CF6* *FF6*
0F9 3F9 6F9 9F9 CF9 FF9
*0FC* *3FC* 6FC 9FC CFC FFC
*0FF* *3FF* *6FF* 9FF CFF *FFF*

Safest web colors[edit]

Designers were often encouraged to stick to these 216 "web-safe" colors in their websites; however, 8-bit color displays were much more common when the 216-color palette was developed than they are now. David Lehn and Hadley Stern have since discovered that only 22 of the 216 colors in the web-safe palette are reliably displayed without inconsistent remapping on 16-bit computer displays. They called these 22 colors the "really safe" palette; it consists mainly of shades of green, yellow, and blue, as can be seen in the table below.[12]

Safest web colors
0 3 6 9 C F
00 *000* *F00*
03 *003* *F03*
0F *00F* *F0F*
F0 *0F0* *6F0* *FF0*
F3 *3F3* *6F3* *FF3*
F6 *0F6* *3F6* *CF6*
FC *0FC* *3FC*
FF *0FF* *3FF* *6FF* *FFF*

CSS colors[edit]

The Cascading Style Sheets specification defines the same number of named colors as the HTML 4 spec, namely the 16 html colors, and 124 colors from the Netscape X11 color list for a total of 140 names that were recognized by Internet Explorer (IE) 3.0 and Netscape Navigator 3.0.[13] Blooberry.com notes that Opera 2.1 and Safari 1 also included Netscape's expanded list of 140 color names, but later discovered 14 names not included with Opera 3.5 on Windows 98.[14]

In CSS 2.1, the color 'orange' (one of the 140) was added to the section with the 16 HTML4 colors as a 17th color.[15] The CSS3.0 specification did not include orange in the "HTML4 color keywords" section, which was renamed as "Basic color keywords".[16] In the same reference, the "SVG color keywords" section, was renamed "Extended color keywords", after starting out as "X11 color keywords" in an earlier working draft.[17] The working draft for the CSS4 color module combines the Basic and Extended sections together in a simple "Named Colors" section.[18]

Color added in CSS 2.1
Name Hex (RGB) Red
(RGB)
Green
(RGB)
Blue
(RGB)
Hue
(HSL/HSV)
Satur
(HSL)
Light
(HSL)
Satur
(HSV)
Value
(HSV)
Alias
orange #FFA500 100% 65% 0% 39° 100% 50% 100% 100%

CSS 2, SVG and CSS 2.1 also allow web authors to use so-called system colors, which are color names whose values are taken from the operating system, for example, picking the operating system's highlighted text color, or the background color for tooltip controls. This enables web authors to style their content in line with the operating system of the user agent.[19] The CSS3 color module has deprecated the use of system colors in favor of CSS3 UI System Appearance property,[20][21] which itself was subsequently dropped from CSS3.[22]

The developing CSS3 specification also introduces HSL color space values to style sheets:[23]

 /* RGB model */
 p { color: #F00 } /* #rgb */
 p { color: #FF0000 } /* #rrggbb */
 p { color: rgb(255, 0, 0) } /* integer range 0 - 255 */
 p { color: rgb(100%, 0%, 0%) } /* float range 0.0% - 100.0% */
 
 /* RGB with alpha channel, added to CSS3 */
 p { color: rgba(255, 0, 0, 0.5) } /* 0.5 opacity, semi-transparent */
 
 /* HSL model, added to CSS3 */
 p { color: hsl(0, 100%, 50%) } /* red */
 p { color: hsl(120, 100%, 50%) } /* green */
 p { color: hsl(120, 100%, 25%) } /* dark green */
 p { color: hsl(120, 100%, 75%) } /* light green */
 p { color: hsl(120, 50%, 50%) } /* pastel green */
 
 /* HSL model with alpha channel */
 p { color: hsla(120, 100%, 50%, 1) } /* green */
 p { color: hsla(120, 100%, 50%, 0.5) } /* semi-transparent green */
 p { color: hsla(120, 100%, 50%, 0.1) } /* very transparent green */


On 21 June 2014, the CSS WG added the color RebeccaPurple to the Editor's Draft of the CSS4 Colors module, to commemorate Eric Meyer's daughter Rebecca who died on 7 June 2014, her sixth birthday.[24]

Color added in CSS4 Colors module
Name Hex (RGB) Red
(RGB)
Green
(RGB)
Blue
(RGB)
Hue
(HSL/HSV)
Satur
(HSL)
Light
(HSL)
Satur
(HSV)
Value
(HSV)
Alias
rebeccapurple #663399 40% 20% 60% 270° 50% 40% 67% 60%

Accessibility[edit]

Some browsers and devices do not support colors. For these displays, or for blind and colorblind users, Web content depending on colors can be unusable or difficult to use.

Either no colors should be specified (to invoke the browser's default colors), or both the background and all foreground colors (primarily the colors of plain text, unvisited links, hovered links, active links, and visited links) should be specified to avoid black on black or white on white effects.[25]

See also[edit]

References[edit]

  1. ^ Niederst Robbins, Jennifer (February 2006). "Appendix D: Specifying Color". Web Design in a Nutshell. O'Reilly. p. 830. ISBN 978-0-596-00987-8. 
  2. ^ York, Richard. Beginning CSS, pp. 71–72.
  3. ^ Guide to Graphics. SPLUS, splus.com. Page 13.
  4. ^ Digital Color Imaging Handbook By Gaurav Sharma. ISBN 0-8493-0900-X
  5. ^ Pemberton, Steven; Pettit, Brad (7 June 2011). Çelik, Tantek; Lilley, Chris; Baron, L. David, eds. "4.2.1. RGB color values". CSS Color Module Level 3. W3C. Retrieved 19 March 2013. 
  6. ^ "HTML 4.01 Specification section 6.5 "Colors"". W3.org. Retrieved 2013-07-08. 
  7. ^ "HTML 3.2 Specification "The BODY element"". W3.org. Retrieved 2013-07-08. 
  8. ^ "Public discussion on SVG mailing list ''Re: color names in SVG-1.0 conflict with /usr/lib/X11/rgb.txt''". Lists.w3.org. Retrieved 2013-07-08. 
  9. ^ Pemberton, Steven; Pettit, Brad (7 June 2011). Çelik, Tantek; Lilley, Chris; Baron, L. David, eds. "4.3. Extended color keywords". CSS Color Module Level 3. W3C. Retrieved 19 March 2013. 
  10. ^ "W3C TR SVG 1.0, recognized color keyword names". W3.org. 2011-08-16. Retrieved 2013-07-08. 
  11. ^ "Browser Display Statistics". W3schools.com. Retrieved 2013-07-08. 
  12. ^ "Death of the Websafe Color Palette?". Physics.ohio-state.edu. Retrieved 2013-07-08. 
  13. ^ "The X11 Color Set". Retrieved 2014-07-06. 
  14. ^ Brian Wilson. "Colors in HTML and CSS". Retrieved 2014-07-06. 
  15. ^ "CSS 2.1 Specification: Syntax and basic data types: Colors". 8 September 2009. Retrieved 2009-12-21. 
  16. ^ "CSS Color Module Level 3 – Proposed Recommendation - 11. Changes". 28 October 2010. Retrieved 2014-07-06. 
  17. ^ "CSS Color Module Level 3 – Working Draft". 18 April 2002. Retrieved 2014-07-06. 
  18. ^ CSS Color Module Level 4 – Editor’s Draft, 26 June 2014
  19. ^ "User interface – System colors". W3.org. Retrieved 2013-07-08. 
  20. ^ Pemberton, Steven; Pettit, Brad (7 June 2011). Çelik, Tantek; Lilley, Chris; Baron, L. David, eds. "4.5.1. CSS2 system colors". CSS Color Module Level 3. W3C. Retrieved 19 March 2013. 
  21. ^ "CSS3 Basic User Interface Module, W3C Candidate Recommendation 11 May 2004: System Appearance". W3.org. Retrieved 2013-07-08. 
  22. ^ Çelik, Tantek, ed. (17 January 2012). "List of substantial changes". CSS Basic User Interface Module Level 3. W3C. Retrieved 19 March 2013. "System Appearance has been dropped, including appearance values & property, and system fonts / extension of the 'font' property shorthand." 
  23. ^ Pemberton, Steven; Pettit, Brad (7 June 2011). Çelik, Tantek; Lilley, Chris; Baron, L. David, eds. "4.2.4. HSL color values". CSS Color Module Level 3. W3C. Retrieved 19 March 2013. 
  24. ^ Glazman, Daniel (21 June 2014). "Re: [CfC] adding 'rebeccapurple' to CSS Color Level 4". Post to www-style mailing list. W3C. Retrieved 24 June 2014. 
  25. ^ "If You Pick One Color, Pick Them All". W3.org. Retrieved 2013-07-08. 

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