Happy, I find that your best bet is to grab the male with the lowest head number, and let him get the entire village pregnant - it works best with high population counts. If your population is maxed, picking a young villager with that head type helps.

Out of all those kids, when they grow up, find the lowest head number again, and repeat. (Or with the original parent, if you're not one of those squeamish about breeding programs in your village.) Even without 'mutant' hair colors, you will creep down the scale - some villagers will be higher on the scale, some lower, but as long as you always breed from the lowest on the scale, you'll get there.