These two portraits were each done in watercolors with three colors each. The first is the very old classical way using only vermilion genuine, vine black and Naples yellow. It is a very fast combination with excellent results. I don't usually use black when I paint but vine black gives a cool blue tone when mixed with white and mixed with vermilion makes a believable dark red. The addition of Naples yellow completes a well rounded set of portrait colors.
Using the 3 primary colors, PY153, PM122 and PB15.3 also works very well but takes more time to mix the usable color. Portraits are very limited in useable colors.
Portraits are one area in paintings where I don't argue against black as much. Landscapes are different, black is not preferred because of the wider range of colors needed. Black in landscapes tends to add a gray pall to all colors it's added to.