Not talking just about deer.
Some animals are white - that is their natural colouring (gulls, polar bears ...)
Some animals change their colouring in the winter, becoming pale (
Stoats ...)
Neither of these are "albino".
Albinism is when most animals of a species are darkly coloured (by melanins or other pigments in their skins, feathers, eyes) but an *individual* lacks the pigment due to a genetic deficiency. The crtitical element, really, is not just that they will have white skin/fur/feathers but that they will lack pigment in the eyes and other places ....