The Chinese people wear' blue gown' (蓝色长袍） in the qing dynasty （清朝）. This is the meaning I am aware of.

it may possibly refer to a graduation gown, but from a generic point of view, no it doesn't have any other meaning I am aware of. Hmm, I just noticed you are studying Korean, maybe "blue gown" has cultural significance in Korean, but not in English. Andrew.