Tail light lens fading
I extracted this information from Mark Etheridge of Moto Guzzi Classics off of the old Topica Loopframe_Guzzi news group (which has now moved to Yahoo!).
If your tail light lens is faded, you can restore the color by boiling it in red RIT dye.
- Boil the dye (a concentrated amount).
- Submerge the lens for a couple of minutes...carefully monitor the progress as you don't want to destroy the lens.