Puh, thats not easy and I have no solution. But think about the conditions the troops were in working those Combat Fatiguee. The jungle, weather conditions, long range under way, it was wet, dirt all aroung on patrols...
I think the greenish grey hue can only be mixed for every new figure in a new way to make them all look different. It is although important WHAT the trooper do in the moment wearing the uniform: Is he in battle, on a patrol, lying in mud, wet grass and so on.
Painting jungle outfits is always an adventure!
Frank