Tobiano - sekelsta/horse-colors GitHub Wiki
Tobiano is a pinto pattern caused by a dominant gene. Tobiano horses often have large blotches of color among large patches of white. Typically all four legs will be white, though the head is often dark. Like other pinto patterns, tobiano can appear on any base color. That means it's possible to have a bay tobiano, black tobiano, red dun roan tobiano, and so on.
The tobiano allele is represented as "To", and the non-tobiano allele is "+".