A horse's colour can be modified or diluted, it can also be covered in part - and sometimes in full - by white patterns.

The genes that control the coloured parts and the genes that control the white pattern are not related and act individually of each other.

White patterns can be separated into two groups:

1. individual white hairs mixed amongst the coloured hairs, commonly referred to as roaning.

2. grouped white hairs that make spots or areas of solid white patches.  

These patterns can also hide characteristics of a horses colour, making it harder to classify them - such as the black legs of a bay or the dorsal strip of a dun.

While the term PINTO actually includes tobianos and overos, many people and societies register Tobianos as Pintos.
While tobiano markings are vertical in direction as shown:  (white goes up or down the body)

Overo patterns, which include Overo, Splash white and Sabino occur in a horizontal direction:  (white goes across the body)