Also, OP - as a few others have pointed out, your foal is a brown based buckskin. The dorsal is caused by foal countershading, which is being intensified by brown's habit of making foals have dark toplines.
Baha. According to Abby's papers, her dam was sired by a black and a sorrel. Turns out that her grandsire, great-grandsire, great-great-grandsire, and great-great-great-granddam are all smoky blacks, with the cream coming from a palomino. Neat!
Yeah, I found pics of her sire. There seems to be a golden/yellow tinge to his pics, but his muzzle looks almost like dark brown instead of grey or black. This is him and the filly.
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