It's a question that i want know, i see that some americans police vehicles have a difference between others, like the car model or the light (strobes or light bar) and principally the painting (the painting on those police cars are amazing).
So, this is the question, no laws about police vehicles?
Here in Brazil, it's necessary to have ONLY red light bars and the state symbol in the car and some others identifications.
And a tip: here we dont have ANY police car model, the state have to buy a civilian model and other company have to modify it.
(sorry for the english)