Here ya go:

http://www.usarmymodels.com/guidetopainting.html

Trousers - Unless they have large cargo pockets on the thighs, you can paint trousers either OD, or a 2:1 mix of MM Leather and MM Field Drab for the brownish woolen trousers. I've also begun using MM Military Brown alone for wool trousers. All trousers with cargo pockets are OD.