I honestly have to say a dark bay, brown or washed out black. If the mare was also that color, I would look at the sire and dam of the mare and see. The only way you can get smokey black is by having a palomino, buckskin or smokey black sire or dam. Smokey black horses tend to be miss represented as bays and browns. If you really want to know, you can get her genetically tested and that will give you the answer. Or... if you have her on allbreedpedigree.com, you could tell me or give me a link and I can give you a percentage estimate of what I "think" might be it. But without the tests I can't be 100% accurate either.