There are three research studies which didn’t confirm it.

In this study, the men gave smaller tips to female servers who wore red.

In the second research, 206 young Dutch men judged the attractiveness of a woman on a dating site. The women wore either a red, black or white shirt. Some men wanted to find a one-night stand, the others a long-term partner. Regardless of context, the woman was not rated more attractive when wearing red.

In the third attempt, researchers achieved the same negative results with 200 Americans.

We have to remember that the red effect can be more significant in real interactions than in the lab with photos. Maybe the color influences the behavior when the person is acting more flirtatiously.

Lynn, M., Giebelhausen, M., Garcia, S., Li, Y., & Patumanon, I. (2013). “Clothing color and tipping: An attempted replication and extension.” Journal of Hospitality & Tourism Research.