What did Green and Dan think of?

Through green and Dan, I thought of spring, everything revived and the grass began to turn green; In autumn, crops mature and maple leaves turn red.

Green and Dan are revelations to life, so the object of this poem is also life. Green represents budding youth, while Dan represents maturity of personality and harvest of life. The evolution of Qing and Dan is only a biased law drawn by the author according to the representative things in different seasons. The first part is Qing and Dan, and the second part is a summary.