• (n.) Abnormal coloration of feathers in which yellow replaces the normal color, as in certain parrots. It is commonly due to lack of the dark pigment which with yellow forms green.
Xan·thoch'ro·ism noun Abnormal coloration of feathers in which yellow replaces the normal color, as in certain parrots. It is commonly due to lack of the dark pigment which with yellow forms green. 
an unusual pigment condition, where birds have yellowish or orange plumage instead of red. If it is caused by diet (as in the case of House Finches) it is not xanthochroism.
Xanthochromism - colouration of an animal that is unusually yellow.