Answer:
Penguins -- all 17 or more kinds -- grow feathers for warmth and for camouflage.
Most penguins have dark, even black backs, so that when viewed underwater from above, they blend into the benthos. As well, most penguins have white chests, for the same reason: when viewed from below while underwater, they blend into the light.
There are also orange, yellow, red, burgundy and other coloured markings on some penguins.
You can read more about penguins, below.