A human face can be broken down into the color bands or zones. In the real world these bands can be extremely subtle. Like most natural observations though, you generally want to exaggerate them as an artist.
"The central zone of the face has more capillaries carrying oxygenated blood near the surface. The forehead, by contrast, is much more free of muscles and red blood cells. And the chin, especially on a man with a black beard, is bluish from the microscopic hairs. Around the lips are relatively more veins carrying blue deoxygenated blood."- James Gurney
James Gurney
MartinGuldbaek
