I sincerely doubt he's bay or black of any sort because his mane, tail, and knees are too brown.
He's definitely not palomino. Even with the darkening from the sooty gene, a palomino could never be that dark.
Also, I don't know if you know this, but he's definitely a sabino. White on the lower lip, blue eyes, large face markings, and jagged leg markings are all characteristics of sabino. The white on the lower lip is a dead giveaway.