Dark Goldenrod

"WhiteSmoke" redirects here. For the computer virus connected with Norton AntiVirus, see WhiteSmoke (Virus).
"Skyblue" redirects here. For the rapper, see SkyBlu.

In computing, on the X Window System, X11 color names are represented in a simple text file, which maps certain strings to RGB color values. It is shipped with every X11 installation, hence the name, and is usually located in /lib/X11/rgb.txt.

Color names are not standardized by Xlib or the X11 protocol. In earlier releases of X11 (prior to the introduction of Xcms), server implementors were encouraged to modify the RGB values in the reference color database to account for gamma correction.[1]

It is not known who originally compiled the list. The list does not show a continuity either in selected color values or in color names, and many color triplets have multiple names. Despite this, graphic designers and others got used to them, making it practically impossible to introduce a different list. In some applications multipart names are written with spaces, in others joined together, often in camel case; this article uses spaces and uppercase initials.

The first versions of Mosaic and Netscape Navigator used the X11 colors as the basis for the Web colors list, as both were originally X applications. The W3C specifications SVG and CSS level 3 module Color eventually adopted the X11 list with some changes.[2] It is a superset of the 16 “VGA colors” defined in HTML 3.2 and CSS level 1.

Color name clashes

Perhaps most unusual of the color clashes between X11 and W3C is the case of ‘Gray’. In HTML, ‘Gray’ is specifically reserved for the 128 triplet, i.e. 50% gray. However, in X11, ‘gray’ was assigned to the 190 triplet, i.e. 75%, which is close to W3C ‘Silver’, and had ‘Light Gray’ at 211 and ‘Dark Gray’ at 169 counterparts. This resulted in W3C’s ‘Gray’, at 50%, actually being significantly darker than ‘Dark Gray’, at 66%.

The W3C also defined a color that is equal to X11’s ‘Green’, but called it ‘Lime’.

Color name X11 color W3C color
red green blue Sample Sample red green blue
Gray 75% 75% 75%     50% 50% 50%
Green 0% 100% 0%     0% 50% 0%
Maroon 69% 19% 38%     50% 0% 0%
Purple 63% 13% 94%     50% 0% 50%

Color name charts

These charts are not a standard set of colors to be found on any X Window system. Rather it is the standardized X11 color names accepted by browsers following W3C standards. This set is cut down and rationalized, and has a few differences from a typical rgb.txt file.[3] RGB values shown are normalised to the 8-bit integer range 0 to 255.

X11/W3C color names
Color Name Hex (RGB) Red

Shades of gray

The list shown above covers only the colors supported by popular browsers. Some browsers like Netscape Navigator insisted on an ‘a’ in any ‘Gray’ except for ‘Light Grey’.

The complete rgb.txt defines 101 shades from ‘Gray 0’ (black) up to ‘Gray 100’ (white) in addition to ‘Gray’ and its variants listed above. The shades are apparently defined by the formula Gray N := round(N% × 255) resulting in e.g. ‘Gray 96’ , which happens to be the same as ‘White Smoke’. Similarly ‘Dim Gray’ is the same as ‘Gray 41’ .

On the other hand ‘Gray’ lies between ‘Gray 74’ and ‘Gray 75’ , ‘Dark Gray’ is not the same as ‘Gray 66’ , and ‘Light Grey’ is not the same as ‘Gray 83’ .

Color variations

For 78 colors as listed above, rgb.txt offers four variants ‘color 1’, ‘color 2’, ‘color 3’, and ‘color 4’, with ‘color 1’ corresponding to ‘color’, so e.g. ‘Snow 1’ is the same as ‘Snow’. These variations are neither supported by popular browsers nor adopted by W3C standards.

The formulae used to determine the RGB values for these variations appear to be somewhere near

color 2 := color × 93.2%
color 3 := color × 80.4%
color 4 := color × 54.8%


  • 205.2 = 255 × 80.4/100 and 192.96 = 240 × 80.4/100 explain ‘Ivory 3’ (205, 205, 196) based on ‘Ivory’ (255, 255, 240).
  • 139.74 = 255 × 54.8/100 and 131.52 = 240 × 54.8/100 are close to ‘Azure 4’ (131, 139, 139) based on ‘Azure’ (240, 255, 255).
  • 237.66 = 255 × 93.2/100 yields ‘Yellow 2’ (238, 238, 0) based on ‘Yellow’ (255, 255, 0).

See also


External links

  • , two specifications of the W3C.
  • X11 rgb.txt 1.2, 2005 (excluding 96 aliases).
  • color picker (.clr) file, with or without duplicate names.
  • Aubrey Jaffer. “Color-Name Dictionaries”. Jaffer’s self-published page includes extensive information about and comparisons between color-name dictionaries.
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