I don't do much 6mm work, but I did take a look at the Leven Miniature's middle east models. I usually start with a beige or khaki base coat, for desert style models, and dry brush out towards a final white dry brushing with a couple of off white and/or lighter khaki shades in between. Of course, a lot will depend on what color you want your models to finish with. If you want to finish with a khaki rather than white look then simply start with a darker base color.
Hope that this helps.