Painting skin tones can be really hard – you want to show the highlights, midtones, and shadows without making the face look flat.
One of the best recent examples I’ve seen of skin tones is by a blogger known as tdylan. The image below is his installation of self portraits, all paintings. Even though it’s his face over and over, you can see that he used different colors in the skin to emphasize highlights or shadows. The top left image uses reds and purples in the darker areas. The top right image uses white and yellow-orange to push the brights. Rarely is black used on its own; more often you will use black to darken a color like red or brown.