Yes, actually the real colour is dark brown, but the vast majority of hair in France is a genetic mixture between brown and blond called chatain in French. However, it is still a bit strange because that dark brown/black colour is the majority colour in Italy and Spain.
What!? Really?? I'm shocked. If I was sitting in the 'Who wants to be....' chair I would have taken a fifty fifty on: London, Paris, New York, and Amsterdam. My biggest bet would have been Paris for sure!
Kerouac, there is also a very large Maghrebi population in France. Some North Africans (especially Kabyles) are chatain, but most have the very dark brown-black of the Mediterranean basin. Of course there are also Sub-Saharan (Black) Africans and Southeast Asians, and recently a significant Chinese immigration, but probably not enough to affect those statistics. Aren't East Asians and related Indigenous Americans the only peoples with truly black hair?
My hair was that very dark black-brown until it turned grey, but I also had a bit of a reddish tinge in the sun or when tanned in the summer, from the Celtic ancestry on one side of my family. I coloured it that "reddish-black", popular among Parisiennes, until I was sick of it and had to do it too often for my hair and scalp health. So now it is silvery with very dark undertones.
I imagine that the "black hair" percentage of French will slowly rise due to immigration, but then again, since mixed relationships are so common in France, many of the children will not have black hair. What will make the difference is the number of black Africans settling in France. I know that at the refugee/asylum center a block away, about 80% of the people in the queue are sub-Saharan Africans. (And some are blond Russians or other eastern Europeans.)
I downloaded a Paris transportation app about three weeks ago and totally forgot about it. My phone just issued two "dinging" sounds and up popped a notice about a Paris transportation strike planned for tomorrow. True?