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Web colors

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Web colors are colors used in designing web pages, and the methods for describing and specifying those colors.

Authors of web pages have a variety of options available for specifying colors for elements of web documents. Colors may be specified as an RGB triplet 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.

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. The origin of the X11 color list is unknown [1].

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. 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

A hex triplet is a six-digit, three-byte hexadecimal number used in HTML and CSS, 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. The hex triplet is formed by concatenating three bytes in hexadecimal notation, in the following order:

Byte 1: red value
Byte 2: green value
Byte 3: blue value

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 24, 68 and A0 respectively in hexadecimal notation. To obtain the hex triplet, we simply write the three hex bytes together without spaces, thus: 2468A0. If a byte is less than 16 (decimal) or 10 (hex) it must be represented with a leading zero to keep the number of digits in the triplet equal to six. For example, the decimal triplet 0,1,2 would be represented by the hex triplet 000102.

The number of colors that can be represented by this system is

Converting RGB to hexadecimal

Converting a decimal RGB value to a hexadecimal value is fairly straightforward. RGB values are usually given in the 0-255 range; if they are in the 0-1 range, multiply the value by 255 before conversion. The number of times this number divides into 16 (without rounding) gives us the first hexadecimal digit (between 0 and F, see hexadecimal if unsure). The remainder gives us the second digit. For instance the RGB value 201 divides 12 times into 16, thus the first digit is C. A remainder of 9 gives us the hexadecimal number C9. This process is repeated for each color value. Most modern operating systems have a built-in calculator to perform conversions between number bases; this can also be done with some calculators. This task can also be carried out with various Internet resources, for instance the website http://www.telacommunications.com/nutshell/rgbform.htm.

HTML color names

The HTML 4.01 specification[1] defines sixteen named colors, as follows (names are defined in this context to be case independent; the table is alphabetically ordered):

Color Hexadecimal Color Hexadecimal Color Hexadecimal Color Hexadecimal
aqua #00FFFF black #000000 blue #0000FF fuchsia #FF00FF
gray #808080 green #008000 lime #00FF00 maroon #800000
navy #000080 olive #808000 purple #800080 red #FF0000
silver #C0C0C0 teal #008080 white #FFFFFF yellow #FFFF00

These 16 were also specified as sRGB and included in the HTML 3.0 specification which noted "These colors were originally picked as being the standard 16 colors supported with the Windows VGA palette." It should be noted that fuchsia is exactly the same as magenta (in the list below) and similarly aqua is exactly the same as cyan. [2]

It should be mentioned that all color values from #000000 - #FFFFFF (16,777,216 colors) are valid.

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. 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.

Almost the exact same color names are used in .NET Framework, in the KnownColor and Color enumerations. The only color difference is DarkSeaGreen which is defined as 8F,BC,8B (instead of 8F,BC,8F).

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), 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.[3]

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. [4] [5]

HTML name Hex code
R   G   B
Decimal code
R   G   B
Red colors
IndianRed CD 5C 5C 205 92 92
LightCoral F0 80 80 240 128 128
Salmon FA 80 72 250 128 114
DarkSalmon E9 96 7A 233 150 122
LightSalmon FF A0 7A 255 160 122
Crimson DC 14 3C 220 20 60
Red FF 00 00 255 0 0
FireBrick B2 22 22 178 34 34
DarkRed 8B 00 00 139 0 0
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
MediumVioletRed C7 15 85 199 21 133
PaleVioletRed DB 70 93 219 112 147
Orange colors
LightSalmon FF A0 7A 255 160 122
Coral FF 7F 50 255 127 80
Tomato FF 63 47 255 99 71
OrangeRed FF 45 00 255 69 0
DarkOrange FF 8C 00 255 140 0
Orange FF A5 00 255 165 0
Yellow colors
Gold FF D7 00 255 215 0
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
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
SlateBlue 6A 5A CD 106 90 205
DarkSlateBlue 48 3D 8B 72 61 139
HTML name Hex code
R   G   B
Decimal code
R   G   B
Green colors
GreenYellow AD FF 2F 173 255 47
Chartreuse 7F FF 00 127 255 0
LawnGreen 7C FC 00 124 252 0
Lime 00 FF 00 0 255 0
LimeGreen 32 CD 32 50 205 50
PaleGreen 98 FB 98 152 251 152
LightGreen 90 EE 90 144 238 144
MediumSpringGreen 00 FA 9A 0 250 154
SpringGreen 00 FF 7F 0 255 127
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
YellowGreen 9A CD 32 154 205 50
OliveDrab 6B 8E 23 107 142 35
Olive 80 80 00 128 128 0
DarkOliveGreen 55 6B 2F 85 107 47
MediumAquamarine 66 CD AA 102 205 170
DarkSeaGreen 8F BC 8F 143 188 143
LightSeaGreen 20 B2 AA 32 178 170
DarkCyan 00 8B 8B 0 139 139
Teal 00 80 80 0 128 128
Blue colors
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
CadetBlue 5F 9E A0 95 158 160
SteelBlue 46 82 B4 70 130 180
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
MediumSlateBlue 7B 68 EE 123 104 238
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
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
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
Grey 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

Another set of 216 color values is commonly considered to be the "web-safe" color palette, developed at a time when many computer displays were only capable of displaying 256 colors. 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 shades each of red, green, and blue (6 × 6 × 6 = 216).

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. Fortunately, there were not radically different palettes in use in different popular browsers.

"Web-safe" colors had a flaw in that, on systems such as X11 where the palette is shared between applications, smaller color cubes (5x5x5 or 4x4x4) 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.

By the early years of the 21st century, driven by the needs of video games and digital photos, personal computers typically had at least 16-bit color and usually 24-bit (truecolor). Even mobile devices had at least 16-bit color, driven by the inclusion of cameras on cellphones. The use of "web-safe" colors fell into disuse, but persisted as folklore.

The web-safe palette system persist as being the palette with the most number of distinct colors, where each color can be distinguished individually by human eyes. This led to the use of web-safe colors in anti-phishing systems. [6]

The "web-safe" colors do not have names, but each can be specified by an RGB triplet. In the table below, a three-digit number is used as a shorthand notation for the six-digit hexadecimal numerals above. (The Cascading Style Sheets language supports both three- and six-digit numerals.) The digit "3" is equivalent to the hexadecimal numeral "33"; "C" is equivalent to "CC". For example, "F63" in the table below is equivalent to "#FF6633" in the system used previously. Below are the values for the 6 shades of each color out of 256 possible color shades.

6 shades of each color
digit hexadecimal decimal
0 00 0
3 33 51
6 66 102
9 99 153
C or (12) CC 204
F or (15) FF 255

The following table shows all of the "web-safe" colors, underlining the really-safe (see next section) colors. The lack of gamma correction means that the six desired intensities 0%, 20%, 40%, 60%, 80%, and 100% are displayed as 0%, 2%, 10%, 28%, 57%, and 100% on a standard 2.5 gamma CRT or LCD, making most colors very dark. The intensities at the low end of the range, especially 0 and 3, are nearly indistinguishable from each other:

Color Table

Web-Safe Colors
*000* 300 555 999 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
036 333 636 936 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*

Really web safe colors

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 and yellow, as can be seen in the table above, where the "really safe" colors are underlined. [7]

CSS colors

The Cascading Style Sheets language defines the same number of named colors as the HTML 4 spec, namely the 16 listed above. Additionally, CSS 2.1 adds the 'orange' color name to the list:

Color Hexadecimal
orange #FFA500

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. This enables web authors to style their content in line with the operating system of the user agent. See [2]. As of early 2004, it appears that the CSS3 color module will once again drop these values, marking them deprecated, but this may change: [3].

The developing CSS3 specification will also introduce HSL color space values to style sheets:

/* 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%) } /* light green */ 
p { color: hsl(120, 100%, 75%) } /* dark 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 */

Accessibility

  • Some browsers and devices don't support colors.
  • For blind and colorblind users, Web content depending on colors can be unusable or difficult to use.
  • Mixing legacy markup like bgcolor with modern CSS fails for legacy browsers not supporting CSS.
  • Both foreground and background color should be modified to avoid black on black effects.

Popular browsers show links as shades of blue, dark background colors like blue or navy don't work for such links. Using CSS to modify link colors cannot work with legacy browsers. The Netscape 4.x support for CSS is frequently disabled for being as paltry as it is.

References

See also