X Window System, X11 Color Names

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. They were defined by Bob Scheifler.

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.

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, as did JavaScript 1.1. 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.'

The chart 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. RGB values shown are normalized to the 8-bit integer range 0 to 255.