While Sam's Hair has been discussed a great deal over the course of the show, not much attention has been paid to Dean's do. Still, it has varied subtly over the seasons. Most notably, when Dean is living with Lisa at the beginning of Season Six, Dean's hair is a bit longer and is worn flattened down and with a part. His hair is also worn gelled down and with a part when he is Dean Smith.
The color of Dean's hair does provoke much discussion - blonde, dirty blonde, brown with blonde highlights or something else? This vexed question resulted in an appearance on Fandom Wank under "People who call him blond creep me out" in July 2010.