slackbuilds/graphics/gcolor2/README

gcolor2 is a simple color selector that was originally based on gcolor,
ported to GTK+2 and fitted with a new user interface. It only requires
GTK+2, so it's not dependent on any specific desktop environment.

It provides the usual color wheel method, input box method, color-picker
method, and the ability to save user-defined colors.

The list of saved colors is initially filled with the definitions read
from /usr/share/X11/rgb.txt.