I have to agree with ajlafleche. I have also won awards at the national level using this same formula. It's simple and one can easily add a few lighter or darker colours to this basic mix to add variety. You just need to remember your colour theory.
For the Native warriors, I think the only point I'd like to add would be to caution people from using too bright a colour for "war paint" on the figure. Native warriors would only have access to pigments that occur naturally. Red as an example, would appear to be a more subddued, reddish brown or orange, which would be arrived at by crushing different plants or minerals to obtain the pigment. More "modern" hues like bright yellows, scarlet and greens would have been difficult to make.
If you'd like, I posted a thread on here entitled "Cheyenne Warrior" just a few posts below this one, that has some pictures of this paint formula in action. Good luck and be sure to share the results!