Betty Beauty is the name of a hair coloring made especially for pubic hair.
Apparently many hair salons have made the practice of providing women with a brown bag of hair coloring to match the coloring they just got put on their heads. A woman named Nancy Jarecki decided why not sell a product like this over-the-counter.

The Betty Story
I hadn’t planned on starting a cosmetics company. But sitting in a hair salon in Rome a few years ago, I made a discovery. As I saw women leaving the salon, I couldn’t help noticing that some would linger by the door. After a few minutes, their colorist would come back with a little paper bag, hand it to them and send them cheerfully on their way.
When I inquired about this mysterious ritual, the receptionist said: “Per sotto, per farli combaciare,” meaning: “For the hair down there… to make it match.” I thought, “How genius… A home coloring kit for the hair down there!” I knew there were no specialized products like this in America.