Your hamster and my hamster could be twins! I've been wondering the same thing about mine. My best guess, based off of this website:
http://www.angelfire.com/wv2/woodvie...iancolors.html
is that he's either a light grey (although it says the undercoat is darker, not lighter), or a sable dominant spot (although it says the blaze on the face is usually lighter, not darker). Neither is quite right based on the descriptions, so maybe someone who knows more about this will weigh in.