Smithsonian Insider – Yellow pigment in penguin feathers is

A description of unique fluorescent yellow pigments in penguin feathers - McGraw - 2007 - Pigment Cell Research - Wiley Online Library

In Case You Were Worried That You'd Forgotten Every Type of Penguin

Why are penguins black and white? – The Tawaki Project

Macaroni penguin - Wikipedia

Yellow-eyed Penguin

Smithsonian Insider – Yellow pigment in penguin feathers is chemically distinct, spectroscopic studies reveal

The Penguin's Palette: More Than Black and White

Meet The Team Jacksonville Icemen

Meet The Team Jacksonville Icemen

Galapagos Penguin from Above