Since the Polar bears have fur that is made up of "hollow guard hairs", polar bears living in zoo's that are in a warmer climate, can have algae growing inside the hollow guard hairs of their fur. This makes them have a greenish tint to their fur. These hollow hairs also keep their hair from matting down when they swim in water.

Polar bear fur is oily and water repellent. The hairs don't mat when wet, allowing the polar bears to easily shake free of water and any ice that may form after swimming. Polar bears gradually moult from May to August, but, unlike other Arctic mammals, they do not shed their coat for a darker shade to camouflage themselves in the summer conditions.

Polar bears look whitest when they are clean and in sunlight, especially just after the molt period, which usually begins in spring and is complete by late summer. Before molting, oils from the seals they eat can make them look yellow.