Today I Learned

Nowadays 青[い] / ao[i] is mostly reserved for blue, except in a few fossilised terms; you'd refer to the greens by 緑 / midori. ("Greens" in both senses - vegs and the colour).

This shift is recent enough to create an issue. International norms require the "go" traffic lights to be green, and when Japan adopted those norms as laws, green was still referred by 青. Nowadays however people understand the word as blue, so...

...you got blue lights. Or rather cyan as a compromise (green enough to fit international norms, blue enough to fit the local law).

Colour differentiation in languages is a fascinating topic. Like, some languages have the same word for green and blue, while some, like Ukrainian, have different words for light and dark blue (similarly to pink and red in English). Also, orange as a color is a relatively new word - it was first used only as a fruit name!

Yeah, but not really. They have a word for green, midori, which is much more common. I think the aoi thing is more historical, but since Japan has has Western education for close to a decade (and yes, even before WW2 they sent people to US to copy methods), there's no generation that grew up without green being green.

Anytime it's used now it's just a hold over from those older times, and to be fair English has it's fair share of antiquated words and phrases.

In Korean "green light" is "파란불" which translates to "blue light / fire" instead of "초록불" this would be "green light / fire. From what I know "초록" the word for green is a relatively new one copied from Chinese, before that it just didn't exist, instead of that blue and green have been mashed together into one.

We do the same btw, Russian distinguishes between light blue (голубой, goluboy) and blue (синий, siniy), treating them as distinct colors. In English, both are often considered shades of "blue."

What most of the resources Im using to learn Japanese have taught me is that it's a very context sensitive language. The same words can have different meanings or spellings just depending on how they are being used. It can be really confusing at times when learning a "new" word that is the same as a previous word, but now it has a different meaning because it's using it differently or spelling it differently.

There's also levels of politeness that change how you might say the same phrase, depending on who you're saying it to. All I know, so far, is the super professional polite way of saying anything; but nothing I watch to immerse myself in the language uses that form, so even phrases I can understand sound a bit different than how I had learned the phrases.

Portuguese and Hungarian have different words for red.

In the novel 1Q84, there's a character named Aomame, which means "green beans".