Almost every skin tone is an earth colour: a muted orange that is lighter or darker, warmer or cooler. So the method is the same for all of them. Mix a base of red and yellow, knock it back with a little blue until it stops looking like orange, then set the value.
Deep skin uses no white
The common mistake with deep skin tones is to start from a light skin mix and add brown or black. That gives a grey, chalky colour. Deep skin is rich, not dark-and-dull: build it from red, yellow and blue at full strength.
Fixing the mix
- Too orange: a tiny amount of blue calms it.
- Too pink: a little yellow. Too yellow: a touch of red.
- Too grey or dead: too much blue. Rescue it with more of the red-yellow base.
- Olive skin: shift the base slightly towards yellow-green with a trace more blue and yellow.
- Deep skin with tubes: build from Burnt Sienna or Burnt Umber with a little Ultramarine.
Light, shadow and warmth
Skin is never one colour. Lit areas are warmer and lighter; shadows are cooler, often with a hint of the complement; and thin skin over the cheeks, nose and ears runs redder. Mix three values of your base before you start, and paint the lights, the middle tone and the shadows from them.
Mix far more base than you think you need, and judge it against your reference, not in isolation. A skin tone that looks too orange on the palette often reads right next to the cool shadows and background around it.
Shortcut tubes
Yellow Ochre, Burnt Sienna and Burnt Umber cover most skin tones with very little mixing. Add them to your paints and the recipes will use them.