Why does the background cloth of the photo need to be red?

In fact, when taking photos in a photo studio, the background cloth can be replaced. Generally, there are several kinds of background cloth to choose from in a photo studio, either according to customers' preferences, or according to the photographer's feelings, or according to the requirements of the photos themselves. It's not necessarily red.

photography as the background is generally made of two materials, cloth or paper, which is commonly called "seamless paper" or "seamless cloth".