This post is not so much about etymology as it is food for thought for anyone who has wondered about or been confused by which word to use for the colours blue and green in Korean.
During your Korean studies, you may have noticed that dictionaries indicate both blue and green for the word 푸르다. Interestingly enough, this phenomenon is not limited to Korean and appears to be quite common throughout languages in Asia, according to the polyglot and language expert Stuart Jay Raj.
The Korean word 푸르다 is related to the noun 풀 (meaning "grass" here), and the definition given in the Korean dictionary on Naver translates to: "A bright and clear colour like that of a clear autumn sky, the deep sea or grass" (맑은 가을 하늘이나 깊은 바다, 풀의 빛깔과 같이 밝고 선명하다). Basically, the meaning of the word is fluid and can in fact be used for both colours.
While context will almost always make it clear which sense of the word is meant, some colour words which may be useful for being more specific are: 하늘색 ("sky blue"), 파란색 ("blue"), 초록색 (草綠色 "grass green") and 녹색 (綠色 "green"). While 파란색 generally refers specifically to blue, one can still find references to the "colour of sprouts or shoots (of plants)" as well as mention of the ambiguous "푸르다" in the Korean definition.
This little investigation has likely raised more questions than it answered, but it is certainly an interesting topic to consider for anyone interested in the fluidity of colour-related concepts across various languages.