Driving with excessively dark tint on your rear windshield, especially if it obstructs visibility, is illegal in most places. Adding a sticker further reduces visibility. While the color of flashing lights doesn't change the legality of the tint, it's highly likely that you could get pulled over for the illegal window tint. The police officer may notice the tint during a routine traffic stop for another reason or specifically target vehicles with what they deem excessive tint.
In short, the blue flashing lights (presumably from police) are not the cause, but the illegal tint is the reason you are *very likely* to get pulled over.
