I had somebody question this. Yes.
It's pretty normal to refer to an animal as "the bay" or "the black" if you don't know the animal's name. Sometimes the sex or breed might be tagged on.
This can throw non horse people who start looking for a noun. Nope, the color is used as the noun - it's perfectly acceptable in the equestrian world. Maybe not entirely correct grammar, but tradition wins out in language.
The grey ;).