Imagine an alien civilisation that has, say, fourteen colours. Calling two adjacent ones by the same name would be as ridiculous to them as someone here calling green and yellow the same thing.

I don't think you need alien civilizations for this. Not all human languages have color words that map 1:1 to English color words. (I seem to recall that the word for "red" in Korean includes what English speakers would call "copper". I could be mistaken.)