Every time I try to talk about the electromagnetic spectrum, I manage to snag my britches on my own pitchfork, as Andy Taylor would say on The Andy Griffith Show. Anyway, above the frequencies used for radio and television waves, but below the x-rays and gamma rays on the spectrum, is the visible segment of the spectrum, where you find our friend Roy G. Biv, i.e. the colors of the rainbow, red, orange, yellow, green, blue, indigo, and violet. Red has the longest wavelength of the colors, roughly 675 to 700 nanometers (or 6750 to 7000 Angstroms, or 0.000027 to 0.000028 inches). Waves longer than those, from 1 to 10 micrometers, are infrared waves, which are handy for TV remotes.
Red is also a hair color, which occurs naturally in roughly 1-2% of the population. Among that 1-2% are my sister-in-law and about half the cousins on the Holton side of the family. When it wasn’t all white or gray, my hair had red highlights in it. Mom always used to say that I should have been a redhead, because, in addition to the red highlights, I have fair skin and lots of freckles and I burn really easily if I don’t use sunscreen.
(And here’s my annual reminder to everyone, regardless of what color your hair is: wear sunscreen. Melanoma is nothing to screw around with. And those of you who like tanning beds, for the sake of your friends and family, please stop using them. They’re more dangerous than the sun. People would rather see you with pale skin than see you in a hospital bed.)
Wikipedia (which earns the title The Blogger’s Best Friend™ every day) has a list of redheaded people. It doesn’t include fictional characters, like Anne Shirley from Anne of Green Gables or Archie Andrews from the comic books, Saturday morning cartoons, and Riverdale. And speaking of Archie, here are The Archies with "Sugar, Sugar."
Natural redheads are almost all of Northern or Northwestern European descent. There are probably more redheads in Ireland than the rest of the world, with Scotland running a close second. There are quite a few in Germany, as it happens, and in Scandinavia. I once heard about a connection between the Vikings and red hair, but most of the sources I saw said that was largely a myth.