About one in 50,000 penguins (of most species) are born with brown rather than black plumage. These are called isabelline penguins, possibly in reference to the legend that the archduchess Isabella of Austria vowed not to change her undergarments (!) until her husband united the northern and southern Low Countries by taking the city of Ostend — which took three years to accomplish. Isabellinism is different from albinism.
Isabelline penguins tend to live shorter lives than normal penguins, as they are not well-camouflaged against the deep, and are often passed over as mates.