This answer sent us into some odd corners of Penn Jillette’s mind, the history of fingernail polish, and a new trend in political statements through fashion.
First, men have been wearing nail polish since around 3200 B.C.E., discovered during an excavation of royal tombs at Ur of the Chaldees (the biblical birthplace of Abraham, believed to be in present-day Nasiriyah, Iraq); evidence from 3000 B.C.E. places nail varnish — made from egg whites, beeswax, and gelatin — on people in the higher classes of China, regardless of gender. In Egypt around the same time, the lower classes wore pale colors, while high society painted their nails reddish brown, with henna. In the 1400s, Aztec and Inca warriors used dyes on their fingernails and in the mid-1800s in France, the world’s first commercial nail salon opened, catering to fashionable men and women to signify cleanliness.
Little is known about how nail polish became exclusive to feminine accessorizing, but by the 1930s, Revlon began using pigments, rather than dyes, in nail polish, which allowed the company to introduce new colors; flappers flocked to them and Revlon and competitors started marketing their lines to women.
Counterculture rock stars, such as David Bowie, Iggy Pop, Lou Reed, and Kurt Cobain, rebelled against gender norms by painting their fingernails (though this writer remembers speculation that it was satanic symbolism), but the trend ended there until recently, when one Elliot Costello introduced the "Polished Man" campaign in which men with one painted fingernail on one hand represent the "one in five children who will be a victim of sexual abuse during his or her life."
Alec Baldwin and Hugh Jackman are celebrity Polished Man supporters. It’s not clear whether or not Brad Pitt and Zac Efron are, though they’ve been spotted with painted nails of late.
As for Penn Jillette, the taller and heftier half of Penn and Teller, magicians and entertainers who've performed together for nearly 40 years, he paints the ring finger on his left hand bright red. Why? Here are the reasons that have been reported over the decades.
The first known reference to it comes from the mid-’80s, when Penn took questions from an audience and a woman asked him why he did it. "For the same reason you do," he responded. (We suppose that meant he wanted to look pretty.)
The April 2002 issue of Nails magazine reported that Penn was "sporting a full set of acrylic nails." Nails quoted Jillete as calling himself as "the world’s slowest drag queen" and stating, "They’re beautiful, they’re strong … I feel bionic."
It means he once shot a man for asking personal questions.
It provides excellent misdirection for a magician.
Because it’s different and adds a little flair.
It’s to remember the day the music died.
Then, for the first time, on the Penn Radio broadcast on November 29, 2006, Jillette began to tell the following story.
When he first started juggling and doing magic, his mother told him that because people were watching his hands, he should make sure his fingernails looked nice. To make fun of her, he painted all his fingernails red. Of course, he couldn’t go on performing with 10 red nails, so he began painting only his left ring finger ("my nicest finger," he claims). Though she didn’t approve, it turned into a tribute to his mom, who died in 2000.
A new idea surfaced in 2012 on the podcast "Skepticality," when Jillette said that he was considering changing the meaning of the red nail polish, telling his daughter Moxie Crimefighter (now 11), it’s for her.
And in case anyone’s dying of curiosity, Penn’s color is Jelly Apple Red (#054) by Essie.
