Masking and or a set of psd layers with different colors seems to be the best way, to me that is. I don't mind throwing a  head texture into any paint app with the a brow psd layers and picking the color or adjusting the color of the choices, then merging and saving. I would prefer the psd option. Unfortunately, there are so many that want it all done for them and even merging a couple of layers is to much work.

I never liked the transmap brows, they never looked very good to me. I have seen so many women with one color of brow and another color hair that it seems normal. a quick example would be Madona, Marilyn Monroe and so on. But I do think it will effect the overall use and sales if a system is not worked out as a norm and not as a bonus.