The bay gene gives a horse black points, black mane, tail and lower legs. Bay genes are dominant over chestnut genes and only one gene has to appear at conception to get a bay foal. When breeding 2 bays, you will have a better chance of a bay foal than a black or chestnut foal because you know both the mare and stud have bay genes and you don't always know what other gene they carry.

A buckskin is a bay horse, diluted by a parent carrying a cream or dilute. This gene takes the red from the bay color and washes it to any shade of buckskin it can. Buckskins by the current genetic standards do not have a dorsal stripe.

A perlino is a bay horse that has a double dilute present (much the same as the cremello dilutes the chestnut gene).  In many cases it is difficult to determine if a double dilute horse is a cremello or a perlino.

Another common misconception is that breeding a perlino horse to a bay horse will guarantee a buckskin. This breeding will insure a dilute, but in most cases you will get about 25% palomino and 75% buckskin from the cross. Unless one of the parents is homozygous bay (carries two bay genes), there is no way to insure a buckskin foal. Since bay is a dominant gene, only one has to be present for the horse to show the trait and only extensive breeding or possibly blood testing can verify if a horse carries two bay genes.

Breeding a cremello to a hertozygous bay will give you 50/50 palomino and buckskin. If the horse is homozygous bay you will get 100% buckskins.

Buckskins also do not breed true. Breeding 2 buckskins will only give you around a 38% chance of producing a buckskin. The rest will be bays, chestnuts, palominos and creams. Odd as it may seem, breeding a bay to a perlino or cream will give you a much better chance of a getting buckskin foal than breeding buckskin to buckskin and breeding a basic color to a buckskin reduces your chances even more.