I fired up my Flash™-enabled browser for that? Blue smoke and mirrors. How about
I remember when people wanted to put a little traffic light in the back window. Green when you're on the gas, yellow when you're off the pedals, and red when you would expect that. Other people threw a hissy-fit over 'safety' and it was deprecated to the third tail-light.
I'm thinking LED replacement taillight assembly with 7 LEDs in a hexagon in the middle replaced by RGB-LEDs. Then the circuit out of a bicycle taillight would hide or show the blue dot—or strobe