Bill Schmoker at Brdpics recently posted a couple photos from the front and back cover of the current issue of The Polar Times. The photos show two pigment challenged penguins. The front photo is a melanistic Chinstrap from Deception Island and on the back cover is an amelanistic captive African Penguin. Bill also provides a link to the Australian Antarctic Division that has a nice collection of penguins with abnormal plumage pigment.
For some photos and comments on unusual penguins I have observed in my travels and some more links to other sites with photos of different looking penguins go here and here.