Who ever gave the advice to mix the opposites of the colors used to make the brown was right on! If you use mostly red and yellow with a litle blue, have them mix a complement using mostly blue, a little red and yellow. Just do the opposite.
For instance, I always tell my students that the reason those hospital gowns are that weird greenish color is because that color is the complement to flesh tone. Every color has a complement or opposite. It is also a "real world use" of color theory. There a lots of those in advertising and merchandising. Often students (and even some teachers I have met) do not understand why they need to know color theory. (not to digress from complementary colors). It is always important to use real world examples for something that seems so esoteric.
Good Luck to all of you who have already gone back.