"The sky is blue and the grass is green" is part of the lyrics in I'm waiting for you at Nalin Lake. It was written and composed by Sun Deming, originally sung by Zhu Yongfei, and released on the whole internet in 2021.
Lyrics excerpt "The sky is blue, the grass is blue, the grass is green, I'm waiting for you at Nalin Lake, the reeds here are the most beautiful, and the lake here is drunk with you drunk with you."