Horse coat genetics?

Okay, I've slowly been learning how genetics work with horse coat colour's but the one thing that's got me stumped is how seal bay works? If anyone is up for explaining that'd be great thank you!

So I'm no pro at genetics, here or in real life, but based on all my horses that have seal brown coats, they require at least one "E" and then an At gene. All of mine are either EE Ata or Ee Ata in their genetics. I don't know if that helps at all, but thats all I know about it c:

the E gene makes sense as it's black based, but i think i'll just keep it at At for the other half as that seems to make sense? thank you!

No problem! You’re welcome to look through my horses and look at the genetics for the seal brown ones, if that helps you. Most all (except a couple young gypsies) have their genetics showing, so that may be a better visual c: 

Seal Brown is made up of these combos:
E_ Ata or E_AtAt