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.

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.

Contents 1 Hex triplet 1.1 Converting RGB to hexadecimal 2 HTML color names 3 X11 color names 4 Web-safe colors 4.1 Color table 4.2 Safest web colors 5 CSS colors 6 Accessibility 7 See also 8 References 9 External links

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 are

An abbreviated, three (hexadecimal) digit form is sometimes used.^[1] 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. However, the three-digit form is not interpreted correctly in some versions of Opera.

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, 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.^[2]

HTML color names

Main article: HTML color names

The HTML 4.01 specification^[3] defines sixteen named colors, as follows (names are defined in this context to be case-insensitive; the table is alphabetically ordered):

Color	Hexadecimal	Color	Hexadecimal	Color	Hexadecimal	Color	Hexadecimal
aqua	#00FFFF	green	#008000	navy	#000080	silver	#C0C0C0
black	#000000	gray	#808080	olive	#808000	teal	#008080
blue	#0000FF	lime	#00FF00	purple	#800080	white	#FFFFFF
fuchsia	#FF00FF	maroon	#800000	red	#FF0000	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." ^[4]

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.^[5]

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. ^{[6] [7]}

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 Amethyst 99 66 CC 153 102 204 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 MediumSlateBlue 7B 68 EE 123 104 238

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

Pixel color depth
1-bit monochrome 8-bit grayscale 8-bit color 16-bit Highcolor 24-bit Truecolor 30/36/48-bit Deep Color
Related
RGB color model Indexed color Palette Web-safe color

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.

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 being the palette with the greatest 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.^[8]

The "web-safe" colors do not all have names, but each can be specified by an RGB triplet. 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 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. The intensities at the low end of the range, especially 0 and 3, are nearly indistinguishable from each other:

Color table

Note that 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.

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. ^[9]

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:

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.^[10] As of early 2004^[update], it appears that the CSS3 color module will once again drop these values, marking them deprecated, but this may change.^[11]

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.

See also

• List of palettes
• Color tool
• List of colors

References

External links

• CSS2.1 Color Specification
• Web colors at the Open Directory Project
• X11/browser colors, with closest web-safe equivalents

Web colors
black	gray	silver	white	red	maroon	purple	fuchsia	green	lime	olive	yellow	blue	navy	teal	aqua