How many colors in a rainbow? Six!
What? Doesn’t “everybody know” there are seven?
No, but seven is what most of us were taught: red, orange, yellow, green, blue, indigo, and violet.
That’s how I learned them in school. We even were taught to remember them using the name ROY G BIV.
Too bad it isn’t really true. Like so many other things we learned in school.
It’s Isaac Newton’s fault. Newton freely admitted – even emphasized – that he didn’t have much of an eye for distinguishing one color from another.
Despite this handicap, it was his famous prism experiments that gave us the so-called “colors of the rainbow” and of what we now call the color wheel or color circle.
His first pass gave the rainbow just five colors – red, yellow, green, blue, and violet.
This didn’t satisfy him. Newton was taken – okay, obsessed – by the notion that a rainbow should have seven colors, corresponding to the seven major notes of the musical scale (do, re, mi, fa, so, la, ti).
Twisting Facts to Fit
To get this result, he stuck in orange (between red and yellow) and indigo (between blue and violet). Hence the sequence we now remember using the ROY G BIV mnemonic.
Perhaps this arrangement isn’t strictly “wrong”. After all, the colors – whether in a rainbow or a wheel – are infinite in number. We can break them down into arbitrary regions and label these any way we like.
The problem with Newton’s seven-color scheme is that it isn’t balanced or symmetrical. The easiest way to see this is by dividing the spectrum into primary and intermediate colors.
Why We Need Balance
Our primary colors are red, yellow, and blue. For discussion, let’s lay these out in a circle (as in a color wheel). Then let’s fill in blank spaces with intermediate (secondary) colors.
Orange goes between red and yellow. Green goes between yellow and blue. Purple (or violet, if you prefer) goes between blue and red. This bring us full circle.
That’s six colors. Where in this scheme does indigo fit? The only logical place is between blue and violet (purple). But this places two intermediates (indigo and violet) between the red/blue primary pair. The other pairs (red/yellow and yellow/blue) have only one intermediate apiece.
This clearly is out of whack. As noted, we can divide up the color spectrum in any arbitrary way we like. But we need to do so in a way that’s consistent.
If we designate three colors as primary, then we need three intermediate colors as secondary. Three, no more or less. Six in all.
I suppose we would pick any five equidistant same-size regions on the color wheel, give them names, and call these primary colors. But then we’d need also five intermediates.
Or we could decide that between each of our primaries (however many we allow) we’ll have three intermediates. Or any other number. We can name these as we like. But if we have three (or 10, or 50) between any primary pair, we need the same number between any other primary pair.
No matter how we slice-and-dice the color spectrum, it’s hard to deny that Newton stuck in indigo where it isn’t needed. And where it isn’t needed, it doesn’t belong.
Thus the basic rainbow (or color wheel) should have six members: red, orange, yellow, green, blue, and purple.
But forget indigo!
And I’m not sure what we’ll do for a memory aid to replace ROY G BIV. Somehow “ROY GBP” hardly seems adequate.
(This article is part of my series on words that are #worth1000pictures.)