I assume you're in the FalloutPrefs.in i file? In that case, the numbers are std. RGB values. They go from 0 to 255. Any decent color picker should have the capability to help you with those.
And just in case you don't have access to a decent "colour picker" this is how they work:
Red | Green | Blue
0, 0, 0 = Black
128, 128, 128 = Medium Grey
255, 255, 255 = White
255, 0, 0 = Red
0, 255, 0 = Green
0, 0, 255 = Blue
255, 255, 0 = Yellow
255, 0, 255 = Magenta (Bright Pink)
0, 255, 255 = Cyan (Bright Blue)
As long as Red, Green and Blue are all equal you will have no colour (White, Greys, or Black).