Thank you for the comments gents. Much appreciated.

Is it indiscreet to ask which paints/triads you used for the khaki ? It looks spot on to me.
Not at all. It's all vallejo paints and I've included the paint codes as I can never remember if they are 'model' or 'game' colour paints. Based on a black undercoat;
Base colour of US field drab (70.873) followed by a mid tone of, surprise, surprise, Khaki (70.988), both of these are straight from the bottle. The highlight is made by mixing the Khaki mid-tone with Dark sand (70.847) in about a 4-1 ratio. Be fairly stingy with the dark sand as it has a tendency to lighten the khaki quite a bit.
I usually do a final edge highlight by mixing a little more dark sand in with the highlight colour. Just to accentuate the edge of the jacket, cuffs and elbows/knees.
I hope that's of some help.

Feel free to ask any other questions if the explanation isn't clear enough.