HOWTO: Choose Paint for your next Paintjob
Here is a slick way to figure out what colors to paint your weapon.
Grab a photo of you Area of Operation. Try to make it a fairly large one photo (large as in terrain covered, not pixel size)
They take it into Photoshop.
Apply the following filter: Pixelate>>Mosaic (set cell size to around 35)
So I can tell that I will want a nice light tan and about 2 types of dark brown and a smidge of OD green or something similar.
If you dont have PS and want to have a photo pixelated, shoot me a PM and I'll whip it out for ya...