Do you mean alternating green and red lamps, or do they flash simultaneously?

Simultaneous flashing means that your remote batteries are weak.

I suspect the alternating flashing, since you say that the car will not start. Alternating lamps on the mirror indicate DAS failure, i.e., you are not considered authorized to start the engine. Probably the most common cause is the K40 relay module, although the ignition switch itself or one of the computers could be at fault.