往事深处少年蓝非比晴空南以浅
[wăng shì shēn chŭ shăo nián lán fēi bĭ qíng kōng nán yĭ qiăn]
It describes someone with nostalgia towards the past and a deep emotional attachment, where the character’s youthfulness (represented by blue) and the clarity of past memories create a complex emotion tied closely to past events.