Ah. Maybe there's a bit of gray in the hi-res shot? But I've had gray hair since I was 30 - let's be honest, it happens. ;) I wouldn't say he looks older than 39 either, but he certainly doesn't look like he looked in the BSG miniseries... nor should he.
(Mind you, I do tend to think most men are at their most attractive between the ages of 36 and, oh, maybe 45 give or take a year or two. So as far as I'm concerned, he's in the midst of his peak. ;) )