Fun fact: 青い (ah-oi) means both green and blue in Japanese. There is a more specific word for green 緑 (midori) but 青い is still commonly used to mean green. For instance, "green light" (as in a stop light) is 青信号 (ah-oh shingou) where 信号 means signal.

This (lack of) B-G distinction also occurs in many languages other than Japanese.

https://en.m.wikipedia.org/wiki/Blue%E2%80%93green_distincti...

"Green" is a reasonable translation - the same word is used for the "green" of plants or traffic lights. When referring to a mountain it is very likely to be referring to its greenery.

The boundaries between named colors have historically varied wildly between languages.

When paired with mountain, I'd say blue is more accurate. 青山 is a fixed term (not quite "idiom" but you get the idea) originated from Chinese.

A fixed term which refers to the lushness and vegetation on a mountain. These are the precise denotations where the word is equivalent to English with "green".

And after a quick search, jisho.org translates that precise set phrase as "lush mountain; green mountain", though with an interesting alternate "burial place" meaning. https://jisho.org/word/%E9%9D%92%E5%B1%B1

And a couple of minutes later another quick search gives me a Wiktionary translation of the Chinese phrase as "green mountains; mountains with lush forests" https://en.wiktionary.org/wiki/%E9%9D%92%E5%B1%B1

You are absolutely right, I meant to say "green" and reply to your parent. I'm embarrassed..