How does white coloured body with black feathers help a penguin in its survival?

Penguins do not have white bodies with black feathers. They usually have black or dark blue backs and white bellies. This colouration provides them with the ability to camouflage themselves. When swimming, their white bellies blend in with the sunlit surface of the sea, while their dark backs are hard to see from below. When on land, the opposite is true - their dark backs blend in with the rocky shore, while their white bellies are hard to see against the sky.