"Cooper" as we call him, is EXTREMELY black in color, but he carries an Agouti, "Aa", meaning he is considered a bay by genetics.  His sire is also BLACK in color and carries the same Agouti.  So, when we call Cooper a very very Dark BLACK BAY, you can easily see why we say this.  He may be one of the darkest, blackish bays you ever lay your eyes on.  When looking at the above photo of him running in the pasture, you see NOTHING BUT Charcoal BLACK!  True Black horses carry an Agouti marker "aa", again Cooper carries one Agouti gene, thus him being "Aa".  So, each horse had 2 Agouti genes.  When you breed a mare to a stallion, EACH horse will throw just one of those two genes to a resulting foal.  True Black horses are "aa", bay's horses are 'Aa".  So when breeding Cooper "Aa" to a black mare "aa", Cooper will throw either his "A" or "a" to the foal, while the black mare can only throw her 'a' to a foal as she has TWO of them.  Your resulting foal when breeding Cooper to a true black mare, will be either  "Aa" [Bay tobiano], or "aa" [Black tobiano} foal. It it just a roll of the dice on what Cooper will throw each time.  However, there is a big chance that he will throw his extremely DARK Blackish-Bay color if he throws his Agouti "A" gene to a given foal.   That color is just gorgeous!!   However you look at him, he is stunning!!!!!!!!!!