Wild Type vs. Mutant Traits
Most populations are polymorphic for most phenotypic traits, from fur color to blood type.
The allele that encodes the phenotype most common in a particular natural population is known as the wild type allele. It is often designated, in genetic shorthand, as "+".
Any form of that allele other than the wild type is known as a mutant form of that allele. Here are a few examples...
Wild type penguins wear tuxedos. Albino mutants look nekkid.
Wild type tigers have orange fur and black stripes. One mutation prevents the deposition of the orange/brown pigment, and the result is a "white tiger" that still has dark stripes. A different mutation prevents any melanin (brown pigment) from forming at all, and the result is an albino tiger.
The "black panther" is actually a mutant version of a leopard (or a jaguar) in which the yellow fur has dense deposits of melanin, making it black. The spots are still there, but harder to see. A black version of any wild type animal is said to be melanistic.
Wild type lagomorphs (rabbits, hares and pikas) and rodents usually have a fur color called agouti. The hair shafts are banded with black/brown/black.
But albino and melanistic forms also occur.