What is the difference between a overo and a tobiano paint horse?

Overo is a white spotting pattern characterized by white body spots on a primarily

colored body at it's lowest expression and at it's highest expression level can produce a nearly white horse.

Horses with moderate white markings generally have color along their top line and on their legs, resulting in the frame version of the pattern.

The OvOv (homozygous dominant) form of this trait results in white offspring that die or have to be euthanized after birth due to a failure in intestinal innervation that prevents normal gut function.