Web colors

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Web colors are colors used in designing web pages, and the methods for describing and specifying those colors.[1][2]

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.[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.

Contents

Hex triplet

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. 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

<math>256 \times 256 \times 256 = 16,777,216</math>

An abbreviated, three (hexadecimal) digit form is sometimes used.[5] Expanding this form to the six-digit form is as simple as doubling each digit: 09C becomes 0099CC. This allows each color value to cover its full range from 00 to FF. 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.[citation needed]

Converting RGB to hexadecimal

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. Most modern operating systems have a built-in calculator to perform conversions between number bases and this can also be done with some hand-held calculators. This task can also be carried out using various web resources.[6]

HTML color names

The HTML 4.01 specification[7] defines sixteen named colors, as follows (names are defined in this context to be case-insensitive; the table is alphabetically ordered):

Template:Colornames

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."[8]

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 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.[9]

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. [10][11]

HTML name Hex code
R   G   B
Decimal code
R   G   B
Red colors
IndianRed CD 5C 5C205  92  92
LightCoral F0 80 80240 128 128
Salmon FA 80 72250 128 114
DarkSalmon E9 96 7A233 150 122
LightSalmon FF A0 7A255 160 122
Crimson DC 14 3C220  20  60
Red FF 00 00255   0   0
FireBrick B2 22 22178  34  34
DarkRed 8B 00 00139   0   0
Pink colors
Pink FF C0 CB255 192 203
LightPink FF B6 C1255 182 193
HotPink FF 69 B4255 105 180
DeepPink FF 14 93255  20 147
MediumVioletRed C7 15 85199  21 133
PaleVioletRed DB 70 93219 112 147
Orange colors
LightSalmon FF A0 7A255 160 122
Coral FF 7F 50255 127  80
Tomato FF 63 47255  99  71
OrangeRed FF 45 00255  69   0
DarkOrange FF 8C 00255 140   0
Orange FF A5 00255 165   0
Yellow colors
Gold FF D7 00255 215   0
Yellow FF FF 00255 255   0
LightYellow FF FF E0255 255 224
LemonChiffon FF FA CD255 250 205
LightGoldenrodYellowFA FA D2250 250 210
PapayaWhip FF EF D5255 239 213
Moccasin FF E4 B5255 228 181
PeachPuff FF DA B9255 218 185
PaleGoldenrod EE E8 AA238 232 170
Khaki F0 E6 8C240 230 140
DarkKhaki BD B7 6B189 183 107
Purple colors
Lavender E6 E6 FA230 230 250
Thistle D8 BF D8216 191 216
Plum DD A0 DD221 160 221
Violet EE 82 EE238 130 238
Orchid DA 70 D6218 112 214
Fuchsia FF 00 FF255   0 255
Magenta FF 00 FF255   0 255
MediumOrchid BA 55 D3186  85 211
MediumPurple 93 70 DB147 112 219
Amethyst 99 66 CC153 102 204
BlueViolet 8A 2B E2138  43 226
DarkViolet 94 00 D3148   0 211
DarkOrchid 99 32 CC153  50 204
DarkMagenta 8B 00 8B139   0 139
Purple 80 00 80128   0 128
Indigo 4B 00 82 75   0 130
SlateBlue 6A 5A CD106  90 205
DarkSlateBlue 48 3D 8B 72  61 139
MediumSlateBlue 7B 68 EE123 104 238
HTML name Hex code
R   G   B
Decimal code
R   G   B
Green colors
GreenYellow AD FF 2F173 255  47
Chartreuse 7F FF 00127 255   0
LawnGreen 7C FC 00124 252   0
Lime 00 FF 00  0 255   0
LimeGreen 32 CD 32 50 205  50
PaleGreen 98 FB 98152 251 152
LightGreen 90 EE 90144 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 32154 205  50
OliveDrab 6B 8E 23107 142  35
Olive 80 80 00128 128   0
DarkOliveGreen 55 6B 2F 85 107  47
MediumAquamarine 66 CD AA102 205 170
DarkSeaGreen 8F BC 8F143 188 143
LightSeaGreen 20 B2 AA 32 178 170
DarkCyan 00 8B 8B  0 139 139
Teal 00 80 80  0 128 128
Blue/Cyan colors
Aqua 00 FF FF  0 255 255
Cyan 00 FF FF  0 255 255
LightCyan E0 FF FF224 255 255
PaleTurquoise AF EE EE175 238 238
Aquamarine 7F FF D4127 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 DE176 196 222
PowderBlue B0 E0 E6176 224 230
LightBlue AD D8 E6173 216 230
SkyBlue 87 CE EB135 206 235
LightSkyBlue 87 CE FA135 206 250
DeepSkyBlue 00 BF FF  0 191 255
DodgerBlue 1E 90 FF 30 144 255
CornflowerBlue 64 95 ED100 149 237
MediumSlateBlue 7B 68 EE123 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 DC255 248 220
BlanchedAlmond FF EB CD255 235 205
Bisque FF E4 C4255 228 196
NavajoWhite FF DE AD255 222 173
Wheat F5 DE B3245 222 179
BurlyWood DE B8 87222 184 135
Tan D2 B4 8C210 180 140
RosyBrown BC 8F 8F188 143 143
SandyBrown F4 A4 60244 164  96
Goldenrod DA A5 20218 165  32
DarkGoldenrod B8 86 0B184 134  11
Peru CD 85 3F205 133  63
Chocolate D2 69 1E210 105  30
SaddleBrown 8B 45 13139  69  19
Sienna A0 52 2D160  82  45
Brown A5 2A 2A165  42  42
Maroon 80 00 00128   0   0
White colors
White FF FF FF255 255 255
Snow FF FA FA255 250 250
Honeydew F0 FF F0240 255 240
MintCream F5 FF FA245 255 250
Azure F0 FF FF240 255 255
AliceBlue F0 F8 FF240 248 255
GhostWhite F8 F8 FF248 248 255
WhiteSmoke F5 F5 F5245 245 245
Seashell FF F5 EE255 245 238
Beige F5 F5 DC245 245 220
OldLace FD F5 E6253 245 230
FloralWhite FF FA F0255 250 240
Ivory FF FF F0255 255 240
AntiqueWhite FA EB D7250 235 215
Linen FA F0 E6250 240 230
LavenderBlush FF F0 F5255 240 245
MistyRose FF E4 E1255 228 225
Grey colors
Gainsboro DC DC DC220 220 220
LightGrey D3 D3 D3211 211 211
Silver C0 C0 C0192 192 192
DarkGray A9 A9 A9169 169 169
Gray 80 80 80128 128 128
DimGray 69 69 69105 105 105
LightSlateGray 77 88 99119 136 153
SlateGray 70 80 90112 128 144
DarkSlateGray 2F 4F 4F 47  79  79
Black 00 00 00  0   0   0

Web-safe colors

Template:Color depth 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 (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 2007, personal computers typically have at least 16-bit color and usually 24-bit (TrueColor). Even mobile devices have at least 16-bit color, driven by the inclusion of cameras on cellphones. The use of "web-safe" colors has fallen into practical disuse, but persisted in culture.

The web-safe palette system persists as a convenient palette whose colors can all be differentiated by human eyes. This led to the use of web-safe colors in anti-phishing systems.[12]

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
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 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 Windows standard 2.5 gamma CRT or LCD, making most colors very dark. (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

In the table below, each color code listed is a short-hand for the RGB value; for example, code 609 is equivalent to RGB 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

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.[13]

CSS colors

The Cascading Style Sheets language defines the same number of named colors as the HTML 4 spec, namely the 16 listed previously. Additionally, CSS 2.1 adds the 'orange' color name to the list[14]:

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.[15] As of early 2004, it appears that the CSS3 color module will once again drop these values, marking them deprecated, but this may change.[16]

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%) } /* 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 */

Accessibility

  • Some browsers and devices do not 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, such as blue or navy, do not display well for such links. Using CSS to modify link colors does not work with legacy browsers. For example, in Netscape 4.x support for CSS is frequently disabled for being rather paltry.[citation needed]

See also

References

External links

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