A growing plant 生 above 丹, a cinnabar well — the colour of new growth named together with the mineral that made pigment. 青 covers a stretch of the spectrum English splits in two: the green of young leaves and the blue of sky and deep water are one colour here.
青 means youth as much as colour: 青年 is a young person, 青春 is the springtime of a life. 青出于蓝 — 'green comes from blue' — says the student surpasses the teacher, from the dye that ends up deeper than the indigo it was drawn from.
A plant GROWING above a well of pigment — the blue-GREEN of new leaves.
青 is the colour of both grass and sky. Chinese did not split green from blue the way English does, so 青 covers both — and 青菜 (green vegetables) and 青天 (blue sky) use the same word.