> If I properly understood, I should download and install the whole X sources
> just to be able to add some colour definitions to the rgb database??? Any
> other ideas?

 You asked for the "proper command to compile rgb.txt". "rgb.txt" comes
with every X11 distribution and is placed in /usr/X11R6.1/lib/X11/rgb.txt

> Still one can not buy it in a version for NetBSD. Right?

 Yes of course you can. But the affordability is another story.

-- 
Markus Illenseer