[munificent]

> current use of "cyan" for blue-green is a modern confusion caused by people who have used Greek words without bothering to check their true meaning.

This is a misunderstanding of how language works. Words don't have any "true" meaning. A word exists to convey an idea from a speaker to a listener. If at that moment the intended meaning is conveyed, that is the word's true meaning at that point in time.

When I say "cyan" and a listener pictures a light color whose hue is around 180° similar to the sky on a clear day, then neither one of us is confused and the correct information has been transmitted from one brain to another.

Whether some long-dead Greeks would have used that same blob of phonemes to convey a different spectral idea is irrelevant. When you said "turquoise", but did you mean to convey "from Turkey"? When you said "beetle", did you mean to convey "little biter" or an insect? Probably not.