My main horse in the game was the white arabian and I named it Andy. (SPOILER WARNING!)

In the epilogue I named it Arthur in memory of Arthur Morgan

Cool

Mine is weednose420

As Arthur, I use an Amber Champagne Missouri Fox Trotter named "Micah".

As John, I use another Amber Champagne named "Arthur".

Dolour

In my second playthrough, I named them Eliza and Isaac