I’ve gotten a lot of use from this list of old & obsolete color names for OSR games. They’re great for naming places, ancient books, etc.
https://www.wordnik.com/lists/archaic-colours
Just attach a color to the name of of something, and you’re set
Porphyrous Ooze
The Pyrrhous Sea
Codex Rubiginous
The Leucochroic Throne
Etc..