Next question is why are some French plates black and some are yellow?
That will be the same as here in the UK, black plates are old and have been phased out for the yellow and white ones, as they were here.
Black plates pre change, yellow white post change.
What happened to the yellow headlights is of interest, i like yellow headlights, i always fancy yellow headlights when i go to france but no one sells the paint you used to get in the good old days.