I believe in Indiana- unmarked cars can pull you over only if the officer is in uniform. If a marked pulls you over the officer doesn’t have to be in uniform.
I was pulled over on a four lane interstate by a state cop, he was mad, said it was disrespectful to pass a cop car- ummmm you’re in an unmarked how was I suppose to know. I don’t look at all cars to see if they have hidden lights.