showrgb - display an rgb color-name database

       The  showrgb  program  reads  an  rgb color-name database from a text file and converts it back to source
       form, printing the result to standard output.  The default database is the one that X was built with, and
       may be overridden on the command line.  Specify the database name without the .txt, .pag or .dir suffix.

/usr/share/X11/rgb  default database.

X Version 11                                        rgb 1.1.0                                         SHOWRGB(1)

       showrgb - display an rgb color-name database

showrgb [ database ]