New History: Never, ever paint anything silver.
It seems like silver paint did make it to Tunisia, most notably on one of the head bearing races. Possibly a fiberglass head race.
“Poor little R2-D2 looked rather bland in his plywood skin, and Bill Harman had the idea to spray him silver. I rushed down in a panic when I heard the silver paint was out. Bill looked at my panicked face as I told him, “Never, ever paint anything silver, John will go mad!” I also hated that look. John Barry and I had a pact: no silver paint would ever be seen on screen. It reminded me of TV science-fiction films where the answer to anything to make it look more ‘spacey’ was to spray it silver. Even worse were the silver material space suits. So Bill, being suitably admonished, threw away all the silver spray cans in the workshop.”
Christian, Roger. Cinema Alchemist . Titan. Kindle Edition.