You have a bay so be creative! You can get away with just about anything!
Personally, I like lime green and purple for my brown mare (not a bay,not a black lol), and dark blue for my small grulla gelding. I will put just about anything on the palomino pony but showed her with blue/purple stuff in jumpers.
Just keep in mind if it's a gelding, no pink..it's degrading for the poor guy lol
Go check out what's available and post a picture of it please..lol