A polar bears hair is hollow which helps it appear white and aids in buoyancy also. It turns yellowish over time when the animal is dead and stuffed.
A good portion of the arctic is actually a desert.
A good portion of the arctic is actually a desert.
Animals living where there is a lot of snow and ice, with sun's rays bouncing off the surface, have several ways of protecting themselves from the light radiation -- one, is to have melanin to absorb the radiation and keep it from getting deeper into the body; another is to have thick, inpenetrable fur, and a third is to have a reflective surface that can bounce away the rays (white, reflective fur such as polar bears').
Eskimos/Inuit may be dark for a couple of reasons. One, because in the Arctic, during the summer the sun is shining 24/7 even late at night. Two, because snow and ice reflect sun rays and intensify exposure. It's not the visible light itself, but the ultraviolet rays (UVA and UVB) that affect the skin.
Interesting about polar bears: they have white fur, but dark skin. I suspect that the fur likely evolved gradually long after the dark skin, as those with the mutation toward increasingly white fur had an advantage in a snowy landscape, concealing themselves from their prey.