| SHOWRGB(1) | General Commands Manual | SHOWRGB(1) | 
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/X11R7/lib/X11/rgb
- default database.