A Actually, there are some basic rules-of-thumb when dealing with color inheritance. These are rules that would apply to any breed, and would be true no matter what other color patterns the horse has.
First, two chestnut parents can only have chestnut foals. But parents of any color combination can have a chestnut foal. The following colors are dominant, and must have one parent of that color or pattern for the foal to show the pattern: grey, roan, tobiano, and dun. It is possible for a horse to produce 100% greys, tobianos, or duns, but it is not possible for a horse to produce 100% roans. (Horses with two roan genes die in utero).
Palominos and buckskin must have one palomino or buckskin parent, unless one parent is black. Black can 'hide' the palomino gene. Silver dapples and silver dapple bays must have one parent that is silver dapple or silver dapple bay, unless one parent is chestnut. Chestnut can 'hide' the silver dapple gene. Cremellos and perlinos must have both parents either palomino, buckskin, cremello, perlino, or black. Cremellos and perlinos produce 100% palominos or buckskins when bred to chestnuts or bays.
Although I haven't given any explanations (that's the complicated part!), these are the basic rules that hobbyists should follow when assigning parents to models. -Lesli Kathman