I think it should look exactly like Spirit. The majority of foals look like their dads to begin with... & it should be a boy. Then they should have a girl with Spirits black markings, Blonde mane, blue eyes. Then her main kanzu, koti color would be white. I think they should name them Destiny & Storm. =)
I think the horse would be gray, with gray hair, Because Spirits colour and rains colour together kinda equal what i said, And it would be a boy named Storm.