coyote TAN, desert tan to some extent, and ACU for effectiveness
if you want realism you can mix and match OD pouches in there lol
the ACU looks alot better for a complete kit...
coyote TAN also works fairly well, mainly because its designed to be standard issue for all US camouflages (woodland, OD, ACU, marpat, etc), I haven't seen many other companies produce it but I know blackhawk makes pretty well everything in coyote tan.
Coyote brown is darker and stands out a bit more from ACU, but it works. Try to get solid color items (like toques and gloves) in foliage green, and don't wear any black because it provides way too much contrast.
I'll post up pics of my LMG vest which will have tan, coyote brown and coyote tan elements, as soon as my pouches get here O_O