Melanin is the primary pigment that determines the color of a bird’s feathers, skin, and eyes. Albinism is an inherited problem caused by an alteration in one or more of the genes that are responsible for melanin producing or it distributing.  Contrary to popular belief, albinos are therefore not necessarily pure white. In an albino of a species with carotenoids as additional color, these pigments remain present. And dependent on the natural location of the carotenoids such a bird will remain completely or partially yellow or red colors.

Our first all-white shafttail female is  offspring of parents with normal/wild plumage color. I'm quite sure mother   is split to isabelle, and father is split to creamino and  isabelle.  The creamino and isabelle mutations in their daughter "work" together to remove from the bird pigment melanin, just as a true albino mutation would. Albino shafttail finches are extremely rare in aviculture.

To get some genetic explanation of albino mutation, click here…and scroll down.