Yeah, it really does work. They don’t like to go places where they cant put on the big showoff thing. And the places who want them are easily found.
Furthermore, such places that put up signage forbidding colors avoid being claimed as turf. It works surprisingly well. The same thing is done with black gangs a dress code prohibiting sportswear.
Of course one or two of that ilk will come in without, but mostly they stay away. Normally its very important to them to strut around and for everyone to know who they are.
That's good! Even bad guys don't go where they're not wanted (or can't impress folks).
Too bad it doesn't work for the "black lives matter" gang. Perhaps they're the dumbest of all. ;-)