Waitresses who wear red earn up to 26 percent more in tips compared to waitresses wearing other colors, according to a new study.

However, the trick for extra tips only works with male customers.

French researchers found that no matter what color waitresses wore, female diners tipped the same amount for service, but men give between 15 and 26 percent extra in tips compared to when the same waitress served them wearing a different color.

The 6-week study, published in the Journal of Hospitality and Tourism Research, consisted of 11 waitresses between the ages of 19 and 26 years old working in five restaurants. Researchers asked waitresses to wear the same kind of t-shirt, but to switch the color of the T-shirt every day.

Past studies also found that waitresses who wore red lipstick or acted more provocatively earned more tips.

Researchers said that the waitresses' make-up and behavior remained the same throughout the study.

The team found that tips were almost identical on days waitresses wore black, white, green, blue or yellow t-shirts, then on days waitresses wore red, the size of their gratuities from male customers inflated by about 15 to 26 percent.

Researchers Nicolas Gueguen and Celine Jacob of Université de Bretagne-Sud said that a total of 722 restaurant customers were included in the study.

Researchers said that the latest findings add to previous findings that link color and attractiveness in women. They said that results from the study suggests that the male patrons may have tipped more favorably to waitresses wearing red because they found that they were more attractive and "unconsciously" may have wanted to be noticed by the waitresses in red.

"The present findings showed that red color was associated with an increase in male patrons’ tipping behavior. Men gave tips more often to a waitress who wore a red tee shirt, and when they did, they gave her a larger amount of money," study authors wrote.

The study authors said that the latest findings may be of interest for waitresses looking to earn an extra buck.

"Our findings have some practical interest for waitresses who want to increase their incomes by increasing the tips left by customers," researchers concluded.

"Color clothing is an easy and inexpensive method to use. As red color has no negative effect on women customers, it could be in their interest to wear red clothes at work," they added.