Pinto-any horse that has large patches of white and any other color.
Tobiano-a pinto horse with rounded markings, white legs, and white across the back from withers to dock. They generally have dark colored heads and a “shield” of dark coloring from the neck extending to the chest. They are usually 50/50 dark and light color.
Overo-essentially, anything pinto but not tobiano. There are several very specific patterns within the overo group, such as sabino, which are not covered here.
Pinto-horse colored like a pinto bean.
Tobiano-the “T” in tobiano looks like a shield, look for the shield marking.
Overo-sounds like “over all”, white markings are generally “over all” the horse.