I certainly over-exaggerated the colors here, but only because there is a truth to it.... bits and pieces that extend from the main mass, such as the nose and ears, tend to have a reddened color to them, they are more susceptible to the elements, thus need more blood (This also accounts for why so much blood comes out when you get a nosebleed) The entire head for that matter, has a lot of blood in it. The head, when compared to the rest of the body has an overall red tone to it.
When skin is stretched over bone, like on the forehead and scalp, it also reddens more, simply for the amount of pressure exerted and exposure to oxygen. The fleshier areas, like the eyebrows and the bags under the eyes, have a blueish tone to them because they don't have the open air exposure that makes the blood red.
The light we have the most exposure to is yellow-orange. Sunlight and incandescent bulbs being the most common sources. The light reflects off of many of the layers, even some of the blue ones, but the red predominates, giving our skin an orange appearance. In pure white light, our skin turns to a pale red-violet. In yellow light, our skin is blue in the shadows, and gradiates to violet then red, orange, and finally yellow.
With merely these colors, and without even changing the intensity, you can create the illusion of light and shadow. The skin also reacts to light differently to light based on the previous qualities. Stretched skin and extended bits are shinier, because they are more pressurized. The shadows on these part are also sharper, less likely to gradiate unless the form calls for it...