Here are some pics that show the many changes that Vasa's go through.......
Breeding season: Male Vasa's have a Hemi-penis
Vasa's Cere and Beak change color throughout the year from white to dark grey.
Vasa's feathers can change color from grey to brown without moulting. (look at Eve's head) Both Males and females go though this change, although this change is most evident in the females.
Vasa Females lose the head feathers during breeding season and their skin and sometimes feet turn yellow. Vasa Males may or may not lose head feathers, and their skin may or may not turn yellow.
(Harold and Maude, look how dark Harold cere is!)
(Eve, Male, with head feather loss)
(Eve,Male, with yellow skin underneath his chin)