I recently bought a secondhand Canon 300mm F2.8L lens for a reasonable price because it had some external paint chip marks & a small ding in the rubber surround.
Optically this lens is amazing, but it looks fairly worn. I read on a photo forum that Halfords can mix up an old Ford colour that's a good match.
Ford cameo beige code no. XSC1658 colour code 0018A
Just got a 100ml bottle mixed up for £9.99 and it is perfect.
It's never going to be spot on because I can't get the dimpled effect but from 2paces away it looks good.
(And the bottle will last for years, but probably not wise to use the supplied paintbrush as it's too big.)