What about Alexis Bledel from Gilmore Girls? She is pretty deep brunette
The thing is, usually the only people with TRUE blue black hair are asian/Indian/Islanders and some Africans. I mean, the other people are brunette, deep, chestnut, dark dark brown hair, but a true blue black is very extreme unless you are an ethnicity that would naturally have true black hair anyway. If you are on the fence with this, go with the darkest cool brown you can get, you will love it.