first of all, the whole deal is fallacious
The vests are not in fact yellow nor even a shade of yellow
The vests are daglo green, a shade of green
I presume the French have no word for the color and substitute yellow
Or the color balance on their cameras suck.
I do have to admit that the color yellow has often crossed my mind when thinking of France. But, this might be changing my mind.
If they roll out the hay carts again, I might start being impressed.
The color Chartreuse comes to mind. Sounds kind of French to me.