[jims4]

Probably best not to use turps or white spirit on them, solvents can degrade rubber and lead to cracking.

Rob, the simoniz back to black spray is just clear silicone based, so would be fine for coloured shells. I've tried back to black, pure silicone spray and autoglym bumper care on mine in the past, all worked but need reapplying now and then.

I much prefer the chalky look these days.