HGG Community Forums

Open genes/normal black color - anyone can breed to them
Restricted genes/orange (I think that's what they're called) - no license required, but they have certain restrictions for breeding and selling
Fantasy genes/purple genes - need to purchase a license to own/buy/breed these horses

DarkPhoenix You have that a bit incorrect.

This information is available on the genetic test results of every horse in the game.
Purple Genes require a gene license to purchase,
Orange Genes can only be purchased privately or via the auction.
Glowing Genes are fantasy genes.

Amber is correct that you can also purchase horses with closed genes if they have been altered.