Originally Posted by Gizmo
I think you are right. I don't think bay could be possible.
It's absolutely possible. There is no way to know the mare's agouti without having her tested. If she's Aa or AA, bay is possible. It's only not possible if she's aa.
The foal has 50% chance of being chestnut, 50% chance of being black OR bay. 50% chance of getting momma's tobiano, and 50% chance of getting daddy's roan, so a 25% chance of both. If the mare is aa, 12.5% chance of a blue roan tobiano. If she's Aa, 6.25% chance. If she's AA, no chance at all.