What colour is a horse with light brown and white patches?

A horse with light brown and white patches is called a bay roan.

Here's why:

* Bay: The base coat color is bay, which means the horse has a brown body with a black mane and tail.

* Roan: The "roan" part refers to the white patches. Roan horses have a base coat color with white hairs mixed in.

So, a bay roan horse has a light brown body with white hairs intermixed, giving it a "roan" appearance. The mane and tail are usually black, though they may have some white hairs mixed in as well.