Matt Stone & Trey Parker?

OK I'm a HUGE fan of south park and matt and trey! I can tell them apart when they are younger (matt has blonde hair and trey has the curly fro..i'm talking like the 90's, late and early) but when I watch newer interviews of them, I can't really tell them apart, I always think Matt is on the left and Trey is on the right? Is there a way to tell them apart? I know which one is matt because of his eyes...