I thought you could only change the yellow flag(c:\soldat\Textures\Objects\flag.bmp)?
It will darken the ctf flags though and white->gray will be yellow.
Tested it :
flag -->
[IMAGE]
result -->
[IMAGE]
looks nice ingame but the blue flag in ctf has turned black and red flag dark red :/
Hmm someone should suggest to use different flag images for ctf, would be nice for WW2 mods.