What do silver China, golden China, yellow China and green China mean?

According to the geographical features of China, a German university professor divided four regions of China. "Silver China" represents the Qinghai-Tibet region, so it is named because of its steep terrain and wide distribution of ice and snow. "Golden China" refers to the northwest region, which is named after its deep inland and desert. "Yellow China" refers to the northern region, where the wheat waves are rolling and the corn is fragrant. "Green China" represents the southern region. Absolute standard answer! ! !