If the police turn their blue lights on, the common citizen would think they were being pulled over. They would believe they were not free to leave. The Florida Supreme Court agrees.
There was a case just decided in Florida and the Florida Supreme Court ruled that flashing police lights detains the person they are aimed at. Our constitution does not allow the police to detain anyone unless they have reasonable suspicion that the person is breaking a law. If the police flash their lights at you for no reason and they eventually find drugs in your car because of the stop, a Jacksonville criminal defense lawyer could move the court to suppress the drugs because the police did not have the right to pull you over in the first place.
In my experience as a criminal attorney in Jacksonville, if the police flash their lights and you pull over abruptly, the police consider that to be a sign of impairment. If you pull over too slow, JSO thinks you are fleeing or eluding them or resisting without violence. No matter what the circumstances, if a marked police car flashed their lights at you, you are not free to go about your business.