Here's a photodump of all the hoof colors in game. Ideally, four of each would be lovely. If anyone finds a type of hoof that is not on this list, please do not hesitate to take a screenshot and send it in!
Black and WhiteEdit
Brown and WhiteEdit
Red Hooves Edit
There are at least three different shades of green possible.
A pony can also have hooves of two (or more?) colors.