Description of problem: The x11 rgb command (used for compiling rgb.txt to add default colors to X) is missing from x11 packages. Searched all RPMs and updates and file does not exist Additional info: It appears (by searching web) that fc2 included the command.
I believe you're mistaken either to the name of the command you're trying to find, or to it's origin, as there is no command in X.Org X11, nor in XFree86 named "rgb". My suggestion would be to join the xorg mailing list to seek technical assistance. Setting status to "NOTABUG"