Sparkly- the bay colors are random, but all from the same genes. So he skipped the grey from mom (which means she is Gg for grey), and inherited the bay from dad (it could also be "under" the grey from mom since grey will override other colors) and randomly got the copper bay.
Lets see... grey was a 50/50 chance from mom. And dad probably was the same with all the genes he had. BUT, I love copper bay and the white pattern he has is so lovely! XD *boops colts nose*