What do you mean by "the river is as green as blue in spring"?

Green as blue: Green is greener than blue. For example, the usage is still "Yu", which means more than. Blue and blue grasses, whose leaves can be used to make blue-green dyes.

Where does this poem come from? How to appreciate?

From the Tang Dynasty poet Bai Juyi's "Remembering Jiangnan Good", this word is about the spring scenery in Jiangnan, and the first sentence is "Jiangnan Good". With a simple and vivid word "good", it includes all the beauty of spring scenery in Jiangnan, and the author's praise and yearning are also included. At the same time, it is precisely because of "goodness" that we can "remember" endlessly. Therefore, this sentence has an allusion to "can you forget Jiangnan" and is related to it. The second sentence "I used to be familiar with the scenery" points out that the "good" scenery in the south of the Yangtze River is not a rumor, but the author's personal experience and personal feelings when he went out to graze in Hangzhou. This not only implements the word "good", but also takes care of the word "memory", which is a wonderful pen and ink to connect the meaning of an article. Three or four sentences vividly interpret the "goodness" of Jiangnan, highlighting the bright colors of jianghua and the red and green rivers, giving people a dazzling impression. Among them, there are contrasts between the same color and different colors, which fully shows the author's good coloring skills. At the end of the article, I collected the whole poem with Can I Forget Jiangnan, which not only expressed the author born in Luoyang's infinite admiration and nostalgia for the spring scenery in Jiangnan, but also created a long lasting charm, which brought the reader into a tearful realm.