Is January a bleak, colorless time of the year where you live? To brighten your gray winter days, we’ve asked Jeopardy! phenom Ken Jennings to poke holes in four of your most embarrassing misconceptions about color. After all, there are plenty of colorful anniversaries to observe this month. The first color TV broadcast was the Rose Bowl of January 1953, and in January 1993, Crayola added sixteen new colors to its crayon boxes, including “Tickle Me Pink” and “Macaroni and Cheese.” The political novel Primary Colors was a January release; so was Radiohead’s album In Rainbows. Could there be a better time of year for a kaleidoscope of facts that—however colorful—are completely wrong?
Color Myth #3: The Deoxygenated Blood in Your Veins Is Blue.
When I was little, I asked my parents once (as I assume most kids do) why the veins in my wrist look blue when the blood inside them is clearly red. I was told, quite straight-facedly, that veins return deoxygenated blood back to the heart and lungs, and deoxygenated blood is actually blue, and not red. This blew my little mind. I asked why I’d never seen blue, deoxygenated blood emerging from any of my various cuts and scrapes, and was told that contact with the air immediately turned blue blood red again. Blue blood was coursing through my body at all times, but I could never see it. I just had to believe in it. It was the circulatory equivalent of the existence of God.
Many children are given this same odd-sounding explanation, which probably comes from anatomical textbook diagrams showing red blood moving away from the heart, and blue blood moving back toward it. But those diagrams are just colored that way for schematic clarity: all blood is red. Deoxygenated blood is a slightly darker red—call it maroon, maybe—but it’s by no means blue. So why do the veins under your skin look blue? It’s not the veins themselves, which are pale and fairly colorless when they’re not filled with blood.
This age-old question was finally answered definitively by a 1996 paper published in the Applied Optics journal, because it turns out that a fairly complicated optical phenomenon is the cause. As red blood vessels get deeper under your skin, their reflectance of red light decreases much faster than their reflectance of blue light, due to the fact that the translucent overlying skin does a very good job at filtering out most of the blue light before it even gets to the vein. If a vein is deep enough (more than half a millimeter), the color that gets bounced back to your eye from its red surface is actually a fairly neutral one, and that neutral color looks bluish to you in comparison to the warmer-colored skin around it. But that explanation is so complex that I’ll probably just tell my kids the same lie I got fed. Think of all the time I’ll save.
Quick Quiz: What veins bring blood from your head back to your heart?
Ken Jennings is the author of Brainiac, Ken Jennings's Trivia Almanac, and Maphead, out now. He's also the proud owner of an underwhelming Bag o' Crap. Follow him at ken-jennings.com or on Twitter as @KenJennings.