I can tell you what will bring it back but it's dangerous stuff, Methylene Chloride. I used it for removing the solid white fade from PVC pipe years ago. The stuff evaporates extremely fast and will almost freeze your hands while using. We would put cloth gloves inside of Nitrile gloves when using. Should be used in a very well ventilated area...preferably outside.
The PVC pipes could be almost solid white from fade, the Methylene Chloride would make the pipes look as if they were extruded that same day.
But...it will absolutely remove the fade.
Probably better on your health just to replace the plastic or repaint!