Install xcolorsel by entering the following commands in the terminal:
sudo apt update sudo apt install xcolorsel
Description:
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.
Version: 1.1a-20
Section: universe/x11