A very interesting circuit to mimic the police's car light flash. The main driver of the circuit is the 555 timer chips and the idea of police's car light flasher is having the light flash alternately and at the same time having vibrating flash.
In the demonstration 100 KOhm potentiometer is added between pin 2 and the electrolyte capacitor connected to the ground to control the flashing speed. Unfortunately no red and blue LED available for this demonstration and forced to use white and green as alternative that make it less convincing. It would have been more realistic if the LED were blue and red.
You may refer to the schematic diagram as below and video of the police car flash.