Web colors

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Web colors are colors used in designing 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 begin with a 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 sixteen 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
ColorNameHex (RGB)Red
(RGB)
Green
(RGB)
Blue
(RGB)
Hue
(HSL/HSV)
Satur
(HSL)
Light
(HSL)
Satur
(HSV)
Value
(HSV)
CGA number (name); alias
 White#FFFFFF100%100%100%0%100%0%100%15 (white)
 Silver#C0C0C075%75%75%0%75%0%75%07 (light gray)
 Gray#80808050%50%50%0%50%0%50%08 (dark gray)
 Black#0000000%0%0%0%0%0%0%00 (black)
 Red#FF0000100%0%0%100%50%100%100%12 (high red)
 Maroon#80000050%0%0%100%25%100%50%04 (low red)
 Yellow#FFFF00100%100%0%60°100%50%100%100%14 (yellow)
 Olive#80800050%50%0%60°100%25%100%50%06 (brown)
 Lime#00FF000%100%0%120°100%50%100%100%10 (high green); green
 Green#0080000%50%0%120°100%25%100%50%02 (low green)
 Aqua#00FFFF0%100%100%180°100%50%100%100%11 (high cyan); cyan
 Teal#0080800%50%50%180°100%25%100%50%03 (low cyan)
 Blue#0000FF0%0%100%240°100%50%100%100%09 (high blue)
 Navy#0000800%0%50%240°100%25%100%50%01 (low blue)
 Fuchsia#FF00FF100%0%100%300°100%50%100%100%13 (high magenta); magenta
 Purple#80008050%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]

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 nameHex code
R   G   B
Decimal code
R   G   B
Pink colors
PinkFF C0 CB255 192 203
LightPinkFF B6 C1255 182 193
HotPinkFF 69 B4255 105 180
DeepPinkFF 14 93255  20 147
PaleVioletRedDB 70 93219 112 147
MediumVioletRedC7 15 85199  21 133
Red colors
LightSalmonFF A0 7A255 160 122
SalmonFA 80 72250 128 114
DarkSalmonE9 96 7A233 150 122
LightCoralF0 80 80240 128 128
IndianRedCD 5C 5C205  92  92
CrimsonDC 14 3C220  20  60
FireBrickB2 22 22178  34  34
DarkRed8B 00 00139   0   0
RedFF 00 00255   0   0
Orange colors
OrangeRedFF 45 00255  69   0
TomatoFF 63 47255  99  71
CoralFF 7F 50255 127  80
DarkOrangeFF 8C 00255 140   0
OrangeFF A5 00255 165   0
GoldFF D7 00255 215   0
Yellow colors
YellowFF FF 00255 255   0
LightYellowFF FF E0255 255 224
LemonChiffonFF FA CD255 250 205
LightGoldenrodYellowFA FA D2250 250 210
PapayaWhipFF EF D5255 239 213
MoccasinFF E4 B5255 228 181
PeachPuffFF DA B9255 218 185
PaleGoldenrodEE E8 AA238 232 170
KhakiF0 E6 8C240 230 140
DarkKhakiBD B7 6B189 183 107
Brown colors
CornsilkFF F8 DC255 248 220
BlanchedAlmondFF EB CD255 235 205
BisqueFF E4 C4255 228 196
NavajoWhiteFF DE AD255 222 173
WheatF5 DE B3245 222 179
BurlyWoodDE B8 87222 184 135
TanD2 B4 8C210 180 140
RosyBrownBC 8F 8F188 143 143
SandyBrownF4 A4 60244 164  96
GoldenrodDA A5 20218 165  32
DarkGoldenrodB8 86 0B184 134  11
PeruCD 85 3F205 133  63
ChocolateD2 69 1E210 105  30
SaddleBrown8B 45 13139  69  19
SiennaA0 52 2D160  82  45
BrownA5 2A 2A165  42  42
Maroon80 00 00128   0   0
HTML nameHex code
R   G   B
Decimal code
R   G   B
Green colors
DarkOliveGreen55 6B 2F 85 107  47
Olive80 80 00128 128   0
OliveDrab6B 8E 23107 142  35
YellowGreen9A CD 32154 205  50
LimeGreen32 CD 32 50 205  50
Lime00 FF 00  0 255   0
LawnGreen7C FC 00124 252   0
Chartreuse7F FF 00127 255   0
GreenYellowAD FF 2F173 255  47
SpringGreen00 FF 7F  0 255 127
MediumSpringGreen00 FA 9A  0 250 154
LightGreen90 EE 90144 238 144
PaleGreen98 FB 98152 251 152
DarkSeaGreen8F BC 8F143 188 143
MediumSeaGreen3C B3 71 60 179 113
SeaGreen2E 8B 57 46 139  87
ForestGreen22 8B 22 34 139  34
Green00 80 00  0 128   0
DarkGreen00 64 00  0 100   0
Cyan colors
MediumAquamarine66 CD AA102 205 170
Aqua00 FF FF  0 255 255
Cyan00 FF FF  0 255 255
LightCyanE0 FF FF224 255 255
PaleTurquoiseAF EE EE175 238 238
Aquamarine7F FF D4127 255 212
Turquoise40 E0 D0 64 224 208
MediumTurquoise48 D1 CC 72 209 204
DarkTurquoise00 CE D1  0 206 209
LightSeaGreen20 B2 AA 32 178 170
CadetBlue5F 9E A0 95 158 160
DarkCyan00 8B 8B  0 139 139
Teal00 80 80  0 128 128
Blue colors
LightSteelBlueB0 C4 DE176 196 222
PowderBlueB0 E0 E6176 224 230
LightBlueAD D8 E6173 216 230
SkyBlue87 CE EB135 206 235
LightSkyBlue87 CE FA135 206 250
DeepSkyBlue00 BF FF  0 191 255
DodgerBlue1E 90 FF 30 144 255
CornflowerBlue64 95 ED100 149 237
SteelBlue46 82 B4 70 130 180
RoyalBlue41 69 E1 65 105 225
Blue00 00 FF  0   0 255
MediumBlue00 00 CD  0   0 205
DarkBlue00 00 8B  0   0 139
Navy00 00 80  0   0 128
MidnightBlue19 19 70 25  25 112
HTML nameHex code
R   G   B
Decimal code
R   G   B
Purple colors
LavenderE6 E6 FA230 230 250
ThistleD8 BF D8216 191 216
PlumDD A0 DD221 160 221
VioletEE 82 EE238 130 238
OrchidDA 70 D6218 112 214
FuchsiaFF 00 FF255   0 255
MagentaFF 00 FF255   0 255
MediumOrchidBA 55 D3186  85 211
MediumPurple93 70 DB147 112 219
BlueViolet8A 2B E2138  43 226
DarkViolet94 00 D3148   0 211
DarkOrchid99 32 CC153  50 204
DarkMagenta8B 00 8B139   0 139
Purple80 00 80128   0 128
Indigo4B 00 82 75   0 130
DarkSlateBlue48 3D 8B 72  61 139
SlateBlue6A 5A CD106  90 205
MediumSlateBlue7B 68 EE123 104 238
White colors
WhiteFF FF FF255 255 255
SnowFF FA FA255 250 250
HoneydewF0 FF F0240 255 240
MintCreamF5 FF FA245 255 250
AzureF0 FF FF240 255 255
AliceBlueF0 F8 FF240 248 255
GhostWhiteF8 F8 FF248 248 255
WhiteSmokeF5 F5 F5245 245 245
SeashellFF F5 EE255 245 238
BeigeF5 F5 DC245 245 220
OldLaceFD F5 E6253 245 230
FloralWhiteFF FA F0255 250 240
IvoryFF FF F0255 255 240
AntiqueWhiteFA EB D7250 235 215
LinenFA F0 E6250 240 230
LavenderBlushFF F0 F5255 240 245
MistyRoseFF E4 E1255 228 225
Gray/Grey/Black colors
GainsboroDC DC DC220 220 220
LightGrayD3 D3 D3211 211 211
SilverC0 C0 C0192 192 192
DarkGrayA9 A9 A9169 169 169
Gray80 80 80128 128 128
DimGray69 69 69105 105 105
LightSlateGray77 88 99119 136 153
SlateGray70 80 90112 128 144
DarkSlateGray2F 4F 4F 47  79  79
Black00 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. Fortunately, 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, driven by the inclusion of cameras on cellphones.[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
KeyHexDecimalFraction
00000
333510.2
6661020.4
9991530.6
C or (12)CC2040.8
F or (15)FF2551

The following table shows all of the "web-safe" colors, underlining the really-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*300600900C00*F00*
*003*303603903C03*F03*
006306606906C06F06
009309609909C09F09
00C30C60C90CC0CF0C
*00F*30F60F90FC0F*F0F*
030330630930C30F30
033333633933C33F33
036336636936C36F36
039339639939C39F39
03C33C63C93CC3CF3C
03F33F63F93FC3FF3F
060360660960C60F60
063363663963C63F63
066366666966C66F66
069369669969C69F69
06C36C66C96CC6CF6C
06F36F66F96FC6FF6F
090390690990C90F90
093393693993C93F93
096396696996C96F96
099399699999C99F99
09C39C69C99CC9CF9C
09F39F69F99FC9FF9F
0C03C06C09C0CC0FC0
0C33C36C39C3CC3FC3
0C63C66C69C6CC6FC6
0C93C96C99C9CC9FC9
0CC3CC6CC9CCCCCFCC
0CF3CF6CF9CFCCFFCF
*0F0*3F0*6F0*9F0CF0*FF0*
0F3*3F3**6F3*9F3CF3*FF3*
*0F6**3F6*6F69F6*CF6**FF6*
0F93F96F99F9CF9FF9
*0FC**3FC*6FC9FCCFCFFC
*0FF**3FF**6FF*9FFCFF*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 and yellow, as can be seen in the table above, where the "really safe" colors are underlined.[12]

CSS colors[edit]

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:[13]

Colors added in CSS 2.1
ColorNameHex (RGB)Red
(RGB)
Green
(RGB)
Blue
(RGB)
Hue
(HSL/HSV)
Satur
(HSL)
Light
(HSL)
Satur
(HSV)
Value
(HSV)
Alias
 orange#FFA500100%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.[14] The CSS3 color module has deprecated the use of system colors in favor of CSS3 UI System Appearance property,[15][16] which itself was subsequently dropped from CSS3.[17]

The developing CSS3 specification also introduces HSL color space values to style sheets:[18]

  /* 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[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.[19]

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. SP LUS, 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). "4.2.1. RGB color values". In Çelik, Tantek; Lilley, Chris; Baron, L. David. 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). "4.3. Extended color keywords". In Çelik, Tantek; Lilley, Chris; Baron, L. David. 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. ^ "CSS 2.1 Specification: Syntax and basic data types: Colors". 8 September 2009. Retrieved 2009-12-21. 
  14. ^ "User interface – System colors". W3.org. Retrieved 2013-07-08. 
  15. ^ Pemberton, Steven; Pettit, Brad (7 June 2011). "4.5.1. CSS2 system colors". In Çelik, Tantek; Lilley, Chris; Baron, L. David. CSS Color Module Level 3. W3C. Retrieved 19 March 2013. 
  16. ^ "CSS3 Basic User Interface Module, W3C Candidate Recommendation 11 May 2004: System Appearance". W3.org. Retrieved 2013-07-08. 
  17. ^ 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." 
  18. ^ Pemberton, Steven; Pettit, Brad (7 June 2011). "4.2.4. HSL color values". In Çelik, Tantek; Lilley, Chris; Baron, L. David. CSS Color Module Level 3. W3C. Retrieved 19 March 2013. 
  19. ^ "If You Pick One Color, Pick Them All". W3.org. Retrieved 2013-07-08. 

External links[edit]