Binary package “xcolorsel” in ubuntu kinetic

display colors and names in X

 xcolorsel is an X utility that displays the contents of the X color list
 file (/etc/X11/rgb.txt) together with tiles showing how the color looks on
 your screen. You can cut the color names/definitions in various formats
 (suitable for resource files or C source) so they can be pasted directly
 into source codes or resources.