Well. Firstly, I'd consider the breeding, conformation, and temperament. Then I'd not even consider breeding until your mare has a show record and can contribute back to a breed. Is she registered?
If she went on to have a show record and does have something to contribute, I'd then consider finances. A pregnant mare and the resulting foal take a large financial and emotional investment.
Lastly, never breed for color. While a pretty little colored foal is tempting, it is better to search for a stallion with a proven show record, nice babies already showing, good conformation and a good disposition. Color is last. Unless of course in breeding paints, then you have even more dangers lurking.
Riding: The art of keeping a horse between you and the ground.