Polar bears appear to be white, but their hair is actually transparent; the white results from light being refracted through the clear hair strands, according to the Animal Diversity Web (ADW), a database maintained by the Museum of Zoology at the University of Michigan. The bears can also be yellowish in the summer due to oxidation, or may even appear brown or gray, depending on the season and light conditions. Polar bear skin is black; it absorbs the heat of the sun to keep the animals warm. Source: livescience