When I was creating a new side account, I was trying to make TB grullos, but both the mare and stallion would not display the picture. For the stallion I chose grullo, but he showed up as bay?
https://horseeden.com/horse.php?id=38452779

that's the horse,

Proof I selected grullo and no grullo image appearing

Mare image too.

I assume as TBs can not be captured with dun? But then why offer grullo. So I think that's the dilemma, no dun TBs can be captured now, but grullo still offered as a base coat

TBs dont come with the dun gene in real life. So you cant get a gen 1 with that gene.

If you get a horse minus the dun gene, shouldn't it be black, as grullo is black dun? Or does it just default to bay if you choose an invalid color?

it just defaults to bay