I like how one of the books from 1971 is titled Compiler Construction for Digital Computers. Very important to make clear this wasn't for analog computers!
Or human computers, but those are horrible to target so I understand if compiler writers would avoid that. The spec is horrible, you never know if your amazingly compiled program will be executed in anyway close to what you wanted. Furthermore, the execution is usually horribly slow.
Would be nice if those colors were also used for category labels by the books easier to memorize and recognize color than two letters