We knew it already but now it's researched another time: waitresses with makeup have more tip than those without makeup.

In this study the effect of cosmetics on tipping behavior and the link between behavior and judgment on the physical attractiveness of waitresses wearing or not wearing cosmetics were tested. A female waitress with or without makeup was instructed to act in her usual way with her patrons. Results showed that the makeup condition was associated with a significant increase in the tipping behavior of male customers. It was also found that the effect of makeup on tipping behavior was mediated by the perception of the physical attractiveness of the waitress, but only when considering male customers.

Read it here
(NB In the earlier research there's a difference in the number of women who tip (or don't) for a waitress with makeup vs no makeup. The CrazyWaiter doesn't have a explanation for that, he emailed the author already for that. Until then: wear make up and give the bill to the men on the table )

I don't know if the title is really true, but apparently they get better tips. Today I talked with collegue E. about the fact that blond girls earn more tips than brunettes and boys, and that it was researched. This year it was researched by a student, Melissa Galm, a 27-year-old finance student at Holy Family University:

Throughout March, they reported their tips from each shift. The two blondes consistently earned more than their darker-haired coworkers. Then on April 1, they all were asked to switch their hair color - blondes going dark, brunettes and redheads going blond - and continue to report their daily take.

One of the blondes was removed from the study because she did not report all her tips and was always dying her hair a different color, Galm said.

Eight of the other compliant nine, however, began experiencing hair bias within a week. All the newly blond waitresses received higher tips, averaging a 5 percent increase. The one blonde who turned brunette, however, saw no noticeable drop in earnings.

Read more at Golden locks: Waitresses' tips rose when hair changed from brunet to blond.

Also a more scientific research by tipguru Michael Lynn showed this relation:

Moreover, the waitresses’ tips varied with age in a negative, quadratic relationship, increased with breast size, increased with having blond hair, and decreased with body size.

So now you wait what to do... dye your hair or be happy with your blond locks!