Here is a repost of an older blog:
So everyone knows their primary colors: red, yellow, blue. As anyone who has been to an art supply store can tell you that there are about 30 shades of each of those colors. Everyone has their own preferences but here are mine:
Quin. coral is a bright pink color, even pinker than the above picture. Undiluted its like Barbie pink. This color is terrific for skin tones. Its a very crisp and clean color that makes for glowing skin tones. I like that its ungranulated, because I don’t think that would look the best as a base for skin tones.
New Gamboge is a very traditional primary. Historically Gamboge was not a permanent pigment, but New Gamboge has been reformulated to have the light fastness that is expected of modern paint. Its a great buttery warm yellow.
Ultramarine is a great go to blue. Its a granulating pigment, which looks good in shadows. This color is very fresh which keeps the darker areas on skin from looking muddy.