Jillaroo:
I have never heard the name that they called this horse, have you TWH or Ozarkgal
HOMOZYGOUS BLACK 4 yr old tobiano stallion available to approved homes.
50% Arabian 50% Sprint Quarter horse. Beautifully marked, approx 15hh.
Beautiful Pinto horse...his breeding as it says is an Arabian/Quarter horse cross..what the Spirit part of the Quarter horse name refers to I have no clue, except maybe it is a bloodline designation.
There is also a color registry where the horse could be registered as a pintabian, since it is a half Arabian that sports a pinto coat. Pinto refers to a horse with a spotted coat color pattern, not a particular breed. He could also be registered in the Arabian Half-Arabian registry. So he could actually be a double registered horse.
Homozygous refers to a genetic equation in which there are two copies of a certain gene present that dictates that all offspring will inherit the particular trait the gene pair is responsible for.
In describing horses as homozygous pertaining to color, it means that all foals the stallion or mare produces will be the homozygous color, such as in the case of this colt, black.
It's a complicated formula that there is genetic testing for, thus allowing a stallion owner to honestly advertise that their stallion is homozygous for a particular color.
Thus if a breeder wanted to breed for a specific color, such as black it is usually guaranteed the foal will be black.
In order for a horse to be homozygous both parents must carry a copy of the gene, so although the resulting foal may be black from a black homozygous stallion, that does not mean the foal will automatically be homozygous as well, unless the dam also carries the gene.
Whew!! More information than you needed? If you are really into the scientific exploration of these genes and how they work to produce color you can further torture yourself at the below website. It has a fairly easy to understand explanation of the gene codes and what colors produce what when XY is bred with YX

.
http://www.grullablue.com/colors/homozygous.htm