Many scientists believe that the penguins' coloration evolved as a means of camouflage. Their black backs blend in with the ocean when seen from above, while their white breasts are difficult to pick out when seen from below. Their solid and heavy bones help them remain submerged in the water.
Penguins are able to keep warm because their feathers and layers of blubber provide good insulation.
Penguins can actually become overheated because the same feathers that keep the heat in also keep it from getting out. Penguins are able to minimize or maximize heat loss by controlling the position of their flippers and feet, and the blood flow to them.