A lot of it will be in gettign the base color selected, then making all the variations of it the various figures require.
Or, you could just do each figure one at a time, and vary how you handle tints and shades.
Having seen piles of unissued WWII uniforms, they were not all that uniform. The khaki color might be more tan, or more green, or more brown than the one on the next hangar. The greens could be very pale, near a sage color with hints of blue, or be more brown, more tan, more olive. (If you can find a mixed jar of Spanish Olives, you can have a good do-by 
.) The darkest green unifomrs used were called "chocolate" for a reason, for having schwartzgrun and olive green hues.