I see... camouflage is one of those things I just sort of guess at when I draw it, but if you're looking for a technique to try, the way I do it involves using two layers. One green, the other brown. Then, I just sort of erase parts of one layer so the other is visible. Trying to keep the shapes rounded is important, most camouflage patters I see in real life use rounded, irregular shapes to appear more "natural", but more modern camo seems to be more detailed in its color variation than what I draw. For cartoons it can be simplified.
Hopefully I explained well enough.