And if you wanted a specific colour within those, you'd have to find a stallion that is, say for blue roan, at least homozygous roan, if not also homozygous black. Even then, you'd have a 50% chance of a bay roan instead of blue roan.
You're better off buying a foal of your colour choice than prowling the interwebz trying to find a genetically correct stud for colour because the majority of the time you'll be sacrificing quality. Plus, you won't have to wait a year for the little one, only to be disappointed in its colour if it's wrong.