What red fortune-telling books are there?

Why do fortune tellers give the scarlet letter black letters? Isn't the novel full of yellow paper and scarlet letters?

In the past, yellow was exclusive to the royal family, and yellow represented the monarch. The meaning of monarch comes from heaven, so the yellow symbol represents providence, while the red symbol has both great joy and great disaster. This is what the ancients said, that is to say, the scarlet letter symbolized by yellow is providence. Now fortune tellers are also innovative. The red symbol is homophonic with Hongfu, and all fortune tellers pray for a good result. So fortune tellers will comfort fortune tellers with red symbols. Black is very eye-catching and nothing special, so now it's all black red symbols.