In extant birds, the portion of the skin that bears feathers (e.g. most of the body) is usually unpigmented or slightly yellow in color. There are some exceptions, among them some chicken mutants pigmented by melanin. The skin does not generally reflect the colors of the feathers. However, the feathers do provide protection from the sun. The skin generally on the body is relatively soft and very loosely attached. That is why birds are so easy to skin. The skin contains numerous types of sensory nerve endings. There is also a set of specialized muscle that allow for the movement of the feathers in the follicle. The posture of the feathers can play a role in theromoregulation. Birds have no sweat gland in the skin.
In the unfeathered portions such as the foot, the face and head the skin may be pigmented or display structural colors (i.e. blue, iridescent, etc). There are various additional structures such as wattles, comb, etc that are colored as well. These have all sorts of functions, may be under hormonal regulation and are actually rather complex structures.
The color patterns of the feathers are independent of the underlying skin.
Hope this helps
Alan H. Brush
M.J. Spring Brush
92 High St.
Mystic, CT 06355