Black TBs are extremely rare.
Foal coat color is notoriously misleading. It used to be a nightmare sending in registration documents when I worked on a breeding farm. Best practice, if you need to know right away, is to clip a patch of hair on his neck and see what color the undercoat is. With a pale foal coat like that; he may also have markings on his legs that aren't visible yet - you can wet the coat on the legs to check for markings.
Of course, the really sensible thing to do, if you don't want to have a full scale foal rodeo with clippers and a wash bucket, is to just wait and see.
Based on genetics and foal coat color; I'm betting on bay.