Hey! I am just now getting into genetics. I have a lovely blood bay stallion and I would love to breed him with mares resulting in more blood bay foals. How is the best way to achieve this? I haven't seen much about blood bays on the forums. Is there colors/coats/breeds I should avoid breeding him with?

Blood bay is just an "optical" color variation for bay here in game.

You can not specifically breed for them. You can just breed for it when you cross bay x bay and hope that the foal is a blood bay.

It can be any other bay variation like "light bay, mahogany bay, copper bay, etc, too!