The complexion of a light-skinned face is divided into three zones. The forehead is a whitish or golden color. From the forehead to the bottom of the nose is reddish. The zone from the nose to the chin tends toward a bluish, greenish, or grayish color.
In real life, these zones can be extremely subtle, almost imperceptible. They are more pronounced in men.
This is an unretouched reproduction of Gilbert Stuart’s portrait of Washington.
Although this chin is covered by a white beard, this portrait of the surgeon Nicolay Pirogov by Ilya Repin shows the first two bands clearly enough.
Women and children don’t have the five-o-clock shadow, but they can be a bit greenish around the lips, and many artists play this up to bring out the complementary lip color. Below, a detail of a portrait by Sargent.
There’s reason behind this. 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.
Like all general rules, there are plenty of exceptions. But it’s good thing to keep in mind next time you’re painting a head.