Katielou your boy is not "grey" that is a common misnomer in Appies. He is Varnish- it has a similar effect to Roan but it is an Appy pattern. If he was Grey he would not show his spots- they would all disappear with the Greying out as it progresses. The blanket on the rump is called that- a blanket. When it is a "snowcap" it means there are no spots evident and the animal is homozygous for the spotted pattern.
This is the end of your PBS -normal Forum business will now be resumed.
TP your foal is at present a Blanket pattern, but my boy, whose picture I put up, was born with just three small white spots in a bay coat- Appy patterns are usually "progressive"