[Tripplethreat]

It has been a law for sometime in my state that a police vehicle used for stops has to be marked with 6 inch high letters.A detective or a task force undercover unit usually calls in a marked patrol unit to make the initial stop,unless it is an extreme emergency. It should be conducted this way throughout the US,so the citizenry will know it's legitimate.
Granted there are some very dark gray DUI task force cars with black lettering that doesn't show up well in day light ,much less at night.
This is, of course, an attempt to hide the car from real violaters while at the same time to be in keeping with the requirements of state law.
I can certainly see where they are coming from with this,but generally a police vehicle used to make any traffic stop should be well marked even if the takedown lights are hidden until put into use.