Join Date: Jan 2010
Location: Gloomy Indianapolis
The light around her muzzle and belly is from a Pangare modifier. It lightens the hair along the bottom line of the horse. Basically the opposite of the sooty modifier, which causes dark hairs along the topline of the horse, that's what creates a mahogany bay.
It was my understanding that a seal brown horse is genetically a bay that doesn't express the black hardly at all. Maybe a tiny bit on the muzzle and hardly at all on the legs, could be wrong though.
As far as the foal color, even if he were to turn gray eventually he wouldn't be gray at birth, it takes years to completely gray out. Could he be black? Often black foal hair is a grayish or buff color until they shed out the first time.