Aston Martin rear lights are probe to leaking causing condensation in the lights, this causes havoc with the LEDs and drivers causing the lights to fail. The lights are poorly sealed from the factory and have a design flaw (Overtightening of the mounting bolts distorts the frame causing more leak)
The usual fix for non-working rear lights is to replace them at approx £1000 each. Most early cars had red rear lights and the DBS and later DB9s had clear rear lights.
Instead of buying replacements I got mine upgraded to sequential rear lights by Davina Tech. Davina Tech replaces the insides of the lights so can upgrade working or damaged lights. The Davina Tech lights have sequential startup and shut down of the tail lamps as well as sequential indicators. They also replace the daft Reversing light (A conventional incandescent bulb built into rear lights that are “sealed”, so when that bulb fails you need to purchase a new light unit)
There are now companies on Ebay that repair the rear lights.