Wisdom
"Saitou, are you sure you don't want to use a spot of dye? You're looking a little silver at the temples."
Pah! Women! Who did they think they were? He was the 3rd Captain of the Shinsengumi! Hair dye! With age came wisdom, as they say, and he was getting all the more wise. His back was still ruler straight, his eyes still as piercing as ever. His hair... Well, there has to be some sense of change.
"Get out of the way, old man!"
On the other hand, perhaps a little touch up would do him good.
