In HS my daughter worked as a server. She's a blond, and she would usually bring home close to $100 in tips, and when she died her hair darker brown her tips dropped in half. A few weeks later when she went back to blond her tips shot right back up more than double.
Another time I was having a conversation with a waitress and we were having a conversation about tipping, and I asked her are there any ways or actions you can take to increase your tips? She said there certainly was. She said she can put gumballs in her shirt and her tips always skyrocket up...