My friends look at me askance when I tell them about this surreal children's picture book I read in a US public library about 1975.
A man (who my brain insists on identifying with Ned Riddle's newspaper comic strip character Mr. Tweedy(1)) visits a prison. I can't recall if the "visit" is as an inmate, a consultant, or just as a visitor.
In the book, the prisoners are all very sad because they spend all day breaking rocks into smaller rocks, and mixing different colored paints into something that invariably turns out dull grey, and as a result all the walls are always dull grey.
Our hero suggests to the warden that they use the colorful paints without mixing them into grey goo.
We end up with a prison whose walls are different bright colors and the prisoners are all much more cheerful.
(1) This was long before the Chicken Run guy.