Roy G. Biv

Many students learn the mnemonic Roy G. Biv to recall the visible colors: Red, Orange, Yellow, Green, Blue, Indigo, Violet. It’s a handy way to quickly remember the order of a rainbow spectrum.

Have you ever asked yourself, “what exactly is indigo?” Is it near blue? Near violet? A mixture of the two? If it’s a mixture of the two, why is it the only ROYGBIV color that isn’t distinct? Can you distinguish indigo from specific shades of blue or violet?

Color physicists have pondered this query. You might be surprised to discover they do not recognize indigo as a real color on the visible spectrum. If that’s the case, how did we end up with Roy G. Biv? You might be blindsided by the answer!

In the late 20th century and the first part of the 21st, seemingly every new scientific discovery comes with a tagline along the lines of “just as Einstein predicted.” The great physicist’s imagination was so vast it continues to dominate the space and quantum age. Rewind just a bit in scope and the name that popped up in Einstein’s time and earlier was Isaac Newton. Indeed, Einstein’s musings on relativity and gravity emerged directly from Newton’s work. As Newton himself intoned, by standing on the shoulders of giants we are able to progress.

Newton is probably most famous today for his work on gravity. The image of an apple falling from a tree and plunking him on the head is one that will probably endure for centuries. But Newton was an extraordinarily broad scientist. In addition to gravitational mechanics, he was also regarded as one of the greatest mathematicians of all time, independently devising the field of calculus. Further, he was a titan in today’s topic: optics. His work, titled Opticks, was a watershed moment in the field.

It is Isaac Newton we have to thank for Roy G. Biv.

Before we arrive at Newton’s involvement in the development of Roy G. Biv, we need to investigate a little about visible light.

What we view as discrete colors are really just points in a spectrum. We can try to define a specific color as a particular wavelength on the visible spectrum, but that designation is arbitrary. Without the aid of those wavelengths, can you pick out exactly on this graphic where “orange” or “green” is?

As you can see, each color we have named really fits into a continuum, not just a single spot.

However, because of the biological makeup of our eyes, we tend to see colors at specific wavelengths. The colors at these wavelengths are called spectral colors. We cannot distinguish wavelengths that differ slightly from the spectral colors. For example, yellow’s spectral band is between approximately 560 and 590 nanometers. We cannot distinguish slight differences above or below that, which blends into orange and green, respectively. We just see yellow

Very few humans can distinguish indigo from blue. Because of this fact, modern color wheels often omit indigo or designate it as a tertiary color. Today, color wheels are often based on six colors. For an artist, the primary colors are red, yellow, and blue; orange, green, and violet are secondary colors. For light, the primary colors are red, blue, and green, while the secondaries are yellow, cyan, and magenta.

The confusing reason for this difference in colors stems from the physical realities of color mixing. The light we naturally see with our eyes mixes in an additive fashion. Red light plus green light equals yellow light. Add all the colors together and you get white. But, if you mix red paint and green paint, you’ll get a weird brown color because the pigments combine in a subtractive fashion. Mix all the pigment colors together and you’ll approach black. These color wheel oddities are tangential to today’s topic, but I figured I would include them because I knew someone would send me a message if I didn’t. The important bit is, in both systems, indigo is not a primary or secondary color.

If we accept that indigo isn’t a big-girl color, why did the great Isaac Newton include it in his rainbow?

His original list only had five colors: red, yellow, green, blue, and purple. As we referenced earlier, Newton was keenly aware of his spot in a lineage of thinkers. Thus, his ideas were part of a spectrum. Going all the way back to Pythagoras, through Aristotle, philosophers believed music and color were connected. In music, seven distinct notes exist, A through G. To match the number of notes in a major scale, Newton added orange and indigo!

Through the gravitas of Newton, the seven colors became the law of the land and Roy G. Biv was born.

Today, physicists understand that only six of the colors comprise the primary and secondary hues. Interestingly, orange makes the cut.

Still, Roy G. Biv is a mnemonic that won’t die. Even DC Comics got in on the saying, creating the character Rainbow Raider, whose real name is Roy G. Bivolo. Comics fans can thank Isaac Newton for his love of classical philosophy and music.