I noticed that Indra and Ashura both had dark brown hair... but then after that the Uchiha had black hair, while Hashirama still has dark brown hair. Don't know if it means anything, if it's meant to be symbolic of Hashirama's will being closer to the originally-intended will of the Sage...?
But then Naruto is blonde and throws the whole thing off lol. Damn you Minato and your lack of an origins explanation.