answer:My dog is a two and a half year old Great Dane and he is already going grey. It might be because Great Danes have a particularly short (8–9 yrs) life span. Plus, his color is blue, which basically means the whole of him is a very dark grey color, so the area around his muzzle is a lighter grey, which makes him look very old. My stepdad has a nine year old Golden Retriever who only recently started going grey.