Depends on the state. You must live in one of the relatively sane ones.

I live in Oklahoma, where it’s either legal or not enforced. Tow trucks, construction vehicles, you name it. Blue lights everywhere. And not turquoise or some other “technically not blue” loophole color, but like “they bought their overhead lights from a cop car manufacturer and stuck it on their roof as is” solid fucking blue.

I hate it.