The 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.
In Ancient Greek, "cyan" was blue, not blue-green. More precisely, it was the color of the pigment "ultramarine blue", which has remained widely used until today. The name of this pigment was already used by the Hittites, long before the Greeks.
An example of a Latin author who distinguished consistently green, blue-green and blue in many places is Pliny the Elder.
Blue was referred to as the color of the sky or the color of the blue pigments used in painting, like ultramarine blue.
Green was referred to as "green like grass", "green like tree leaves" or "green like emeralds".
Blue-green was referred to as "green like the littoral sea", "green like turquoise" or "green like beryls".
This is especially obvious in the discussion about emeralds and beryls, which are identical but for their color, the former being green and the latter blue-green.
Similarly, in Latin "red" was used for both red and purple, but the two colors were distinguished as "red like crimson dye" (beetle-based dye) and "red like purple dye" (snail-based dye).
Someone has downvoted this, despite the fact that what I have written is not an opinion, but just facts.
Because I have seen on HN extremely frequently downvotes that just show that the downvoters are ignorant about what they downvote. I stopped a long time ago to downvote comments.
Now I either upvote when I agree and otherwise I write a comment explaining why I disagree.
It would have been better if others had followed such a policy.
Perhaps the downvoter had something to say about "cyan", but this is indeed only one example of a long list of Ancient Greek words that have been borrowed into English during the 19th and 20th century, but which are used with incorrect meanings. Most likely this is due to the fact that those who have introduced these words did not study the Ancient Greek language and they also did not consult anyone knowledgeable or any good dictionaries. Another example of this kind is "macro" used as an opposite for "micro", i.e. as "big", while the true opposite of "micro" is "mega" = "big", while "macro" means "long", the opposite of "short" ("brachy" in Ancient Greek).
moritzwarhier
today at 8:26 AM
I found this an interesting "actually...", not sure why you're being downvoted.
Ofc the modern usage is not necessarily a "confusion" because of an older meaning, maybe that's bothering people, but I read it as tongue-in-cheek.
I prefer "turquoise" anyway, which is more common in German for blue-greenish colors.
There is no doubt that confusions are the origin of these English words.
It is extremely unlikely that any of those who introduced these words in English chose intentionally to use them for other things than for what they had been used for millennia.
For a modern user, it is no longer a confusion to use such words in their currently widespread sense. When speaking to others, I also use such words with their current meaning, in order to be understood.
Nevertheless, it is good to know their original meanings, especially when reading older texts, which may use those meanings. I have seen a lot of ridiculous claims about texts written in the Antiquity, or even about some texts written a couple of centuries ago, where those who had read those texts had been mislead by believing that the words had the same meaning as in modern English.
Especially about the colors known by ancient people, e.g about the Ancient Greeks, there have been many fantastic theories, e.g. that the Ancient Greeks did not know blue or brown, when already in the Iliad of Homer there are a lot of instances of words meaning "blue" (= "the color of the ultramarine blue pigment") or "brown" (= "the color of burnt wood").
moritzwarhier
today at 9:25 AM
Fair!
Thanks for elaborating. So not tongue-in-cheek at all.