NAME
showrgb - uncompile an rgb color-name database  
SYNOPSIS
showrgb [ database ]  
DESCRIPTION
The showrgb program reads an rgb color-name database compiled for use with the dbm database routines 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 .pag or .dir suffix.  
FILES

/usr/X11R6/lib/X11/rgb
    default database.