I just looked on Jim Breen’s WWWJDIC and it appears that it does have secondary meanings of pale and inexperienced. Interesting. Thanks for pointing that out.

You may be right. I haven’t enough knowledge to say one way or the other.

I’ve run into this off and on over the years, along with several hypotheses which have readily-available counterexamples. If one searches Google Images for 青い, there are plenty of examples of light and darker blues.

Perhaps those should be more technically classified 藍 (あい, indigo). I don’t know. My Japanese friends haven’t an answer either. To them those colours are all 青い. They don’t make the distinction that you point out. Perhaps in universities Japanese language professors might quibble about the distinction as academics everywhere are apt to do.

My current belief (based on admittedly thin knowledge and flimsy evidence) is that the Mediaeval concept of 青い was different, along the lines of what you say. I also suspect that it’s a concept that bled over from Chinese because it overlaps with what I heard years ago from Vietnamese friends. Back in the 1980′s I had some close contact with the Vietnamese culture. I was told that they didn’t used to have a clear distinction between blue and green. One Vietnamese friend said the confounding of blue and green came from Chinese influence on the language. I don’t know enough about the Chinese language and its etymology to judge how true that may be. However, if true it would explain the commonality.

I further suspect that any distinction resides in academia, and not among ordinary people.

I’m not hung up on the reason, but find it interesting. Etymology for every language has its curiosities. If it were all clear, logical, cut and dried… where would the delight in wondering go?

Anyhow, enough of my rambling nonsense.

Thanks again for sharing your thoughts!

“Blue” in English language often includes navy blue and light blue, which are closer to purple in colour spectrum.

While in Japanese culture, navy blue and light blue are not considered as blue.
In Japanese, blue is general term for blue that is much closer to green in colour spectrum, but often only used for the color of light.
When Japanese people are looking at actual green paper, they don’t say “blue paper”, but when people are looking at green lights in general, they do say “blue light”