Skin is semi-translucent and hard to get right.   The secret is studying skin in natural light and looking for the cooler colored areas.  I'm surprised by how many young artists neglect that.  I see all kinds of figure paintings with caucasian skins colored Kodak orange.  Our painter ancestors were able to get wonderful effects with very limited means.  Peter Paul Rubens painted most of his magical flesh effects using only a yellow ochre, a dull red, black and white.