Why do penguins have yellow on them?

Question

I can underastand why a Penguin is black and white because they blend in with their environment. But why do they have a little bit of yellow on them?

Answer 1

king and emperor penguins have yellow on the breast and neck. Crested penguins have yellow crests over the eyes. They are used for display purposes

Answer 2

Though I don't know, my guess would be the same as the reason that male cardinals are red: sexual selection. The penguin who can survive in the wild, despite flashiness, is obviously strong, fast, and healthy, and therefore will likely have strong, fast, healthy babies.