Before you start your first figure painting or portrait, you need to gain control of the colors you're going to use. Paint up a value scale on a small piece of paper or card, gradually shifting light to dark.
Make a note of what colors you use and in what proportions at the bottom of the scale (or on the back when the paint has dried). With practice, this color-mixing information will become instinctive. Knowing how to mix the range of skin tones means you can concentrate on painting, rather than interrupting your painting to mix the right tone.
It's helpful to have a gray value scale to hand when you paint a skin-tones value scale to judge the tones of each color you mix. Squinting your eyes at your mixed colors also helps in judging how light or dark its value or tone is.
When painting from a model, start by establishing the range of tones in that particular person. It's likely that the palm of their hands will be the lightest tone, a shadow thrown by the neck or nose the darkest, and the back of their hands the mid-tone. Use these three tones to block in the main shapes, then broaden out the range of tones and refine the shapes.
