大家好! Hi everyone! I was reading a chinese text when I found this phrase: 青出于蓝而胜于蓝. I know the meaning is "the pupil surpasses his teacher" or "the young generation surpasses the old one", but I don't understand why 青(dark blue) become 'pupil' or 'young generation' , and why 蓝 (light blue) become 'teacher' or 'old generation'. What's the connection? 有人能解释给我一下吗? Thank you in advance and sorry for my bad English.