I understand the “color wheel” is a man-made concept, and that red and violet never meet in the light spectrum. They are just the beginning and end of the visible color spectrum, seen in a rainbow. I was just referring to how it could be better represented as a concept if 6 colors were used, and not 7. The “color wheel”, while incorrect from a light wavelength POV, would show the correct color between red and blue.
However, you have a point. Let’s take the color wheel out of this discussion, and just punt indigo!
“No Pluto, no Indigo!” (Bumper stickers and t-shirts will be available soon in the gift shop).
There’s something I need to get off my chest guys.
Many years ago I was attending “trivia night” at Rockhoppers restaurant. The trivia hostess asked the question, “What are the three primary colors.” I said red, green, and blue.
The trivia hostess later announced it was red, yellow, and blue. I approached her about this answer, but she basically called me an idiot and said every first grader knows its red, yellow, and blue.
I devote a chapter in my book to precisely the topic of why there are seven colors in the rainbow.
The short answer – it’s Newton’s And Newton really is the first person to suggest there are seven colors in the rainbow fault, but not because of the “mystical” properties of the number seven.
In his first draft of Opticks Newton talked about only FIVE colors in the rainbow, and he wasn’t scrupulous about changing things, so those passages are still in there, alongside ones that talk about seven colors. The two he left out were orange and indigo.
What seems to have c hanged his mind was his seeing the analogy to the musical scale. Although Newton didn’t believe in the wave nature of light, he definitely associated characteristic lengths with the colors. You can see this in his treatmernt of the phenomenon called “Newton’s rings”, where he saw interference effects between light reflected from a spherical glass surface placed on a flat glass surface. He could calculate the distances between the surfaces and associate it with the color (although, not believing in waves, he didn’t see this as wave interference). What’s more, after you went through one series of colors, it would repeat with another set of colors, and then another. It was just like the way the notes on a piano go from one octave to another, from C through D, E, F,G, A, and B back to the C and octave higher.
On a piano or a harp, the tone of the note was associated with the length, and in classical tuning there are distinct mathematical relationshiops between the notes"D" uses a string 8/9 as long as “c” in classical tempering, “E” is 3/4 as long, and so on, until a string half as long gives you the “C” of the next octave.
Well, Newton had lengths associated with the colors, so he compared those with the ratios for musical notes and – mirabile dictum – they were the same! Only now he hade a problem with his five color spectrum, because there are seven distinct notes in the octave, ignoring the top note C, D, E, F. G. A, and B, ignoring the upper C. Or Do Re Mi Fa Sol La Ti (and then to the next “do”)
(You can stop singing “Doe, a Deer” in your head now.)
Newton’s use of five colors oprobably comes fro his looking at the interference phenomenon of Newton’s Rings in white light, for which the orange isn’t so obvious and indigo is part of that whole bluie-violet run. So he looked at light from his prism, or from the rainbow, and realized , while red and yellow fit pretty well for lower “Do” and “Mi”, he needed a different color for “re”. Well, that was yellow in his prism-produced spectrum. He had a harder time with “La”, which had to fall between blue and violet. To me, I don’t see a different named color in there. But Newton decided there was, and called it “Indigo”, and interviewed his friends, trying to get them to agree that “indigo” was really, really a different color than blue. I’ll bet this made him even less popular than he already was.
“Indigo” is the plant coloring that makes blue jeans blue. There’s a reason we don’t call them “indigo jeans”. Most people just don’t see the difference. If you look at those “rainbow” flags, you;'ll notice that they either only have six colors (no indigo), or else substitute a light blue (which DERFINITELY isn’t indigo) for the seventh.
There are, of course, virtually infinite gradations across the spectrum. We simply don’t try to name them all. It’s a good thing that Newton didn’t take the full chromatic scale as his model – using the black keys as well as the white keys, or else we’d need five more color names, with another, for instance, between red and orange.
So has anyone taken a stab at presenting music visually with each colour represented by a note?
Combine that with a lissajous generator and I think it might be worthy of a laser show…
Not as far as I know. I’ve considered the possibility of a Rainbow symphony, but lack the musical chops to compose one.
When Philip Morison did his PBS series “The Ring of Truth” back in 1993, he explained the different colors as having different wavelengths while sitting at a piano keyboard that had the keys of the octave at middle C painted in the colors of the spectrum as a clever way to illustrate the concept. I don’t know if he was aware of Newton’s derriving his colors on the same basis, but it’s the closest I’ve seen to anyone drawing the analogy between music and color, and playing an instrument at the time.
Okay, since I posted in this thread last I think I’ve come up for a rationale why there should be seven colors in the visible spectrum; not necessarily the classical seven, but still seven:
There are typically three kinds of color-sensitive cones in the human eye. If you map sensitivity of each versus wavelength, you’ll get three rough bell curves A B & C, each overlapping with the curve next to it at least. The A and C curves might also overlap a little, but that’s not really important.
Assign one named color to the highest point on each curve. That’s three.
Assign named colors to the range where A and B are approximately equally sensitive, and similarly where B and C intersect. That’s two more, total of five.
Finally, assigned named colors to the “outer slopes” of curves A and C, where they’re still sensitive but the furthest from any other color. That gives us a total of seven.
But when we try to assign names, the two reddest colors become problematic. Do we make the peak of the red-cone curve “Red” and use “Maroon” or “Rust” or something else for the part of the spectrum where red shades to infra-red? Or use “red” for the reddest and “orange” for the peak of the red sensitivity?
Then you’d have yellow, green, aquamarine/turquoise/cyan, blue, and violet.
You can come up with any sort of reason you want, but “classical” seven, as I say, only goes back to Newton. There have been other color numberings in the past – 4 or 5, but the only other ones to posit seven colors were Medieval artist Cennino Cennini (whose seven colors included White and Black, which we wouldn’t call “colors”) and 16th century theorist Franciscus Maurolycus, but I distrust the evidence in his case.
Newton, as I say, chose his by analogy with musical tones. But there’s really no reason for choosing any number of colors – they don’t have to align with the number of distinct color sensors in our eye or the number of their intersections. Choose ten equally-spaced colors from least to most sensitive, if you wish.
This post is freaking brilliant. If you can get on board with making the two red colors red and orange, then we have the scientific rationale in place for the Red-Orange-Yellow-Green-Cyan-Blue-Violet revolution.
Roy G. Cbv says: No indigo!
I’ll start making the flyers and printing the T-shirts.
Who says there hasn’t been? I learned ROYGBP in kindergarten, if not earlier, and didn’t hear of this funny “indigo” thing until high school. I expect many other folks have had the same experience. Is what one learns in high school necessarily “more official” than what one learns in kindergarten? If anything, I’d be inclined to argue the opposite.
Right, which is why it’s a shame it’s still taught to students when we know better, and such pigments are not only readily available, but a standard in color reproduction.
CMY is a huge improvement over RYB.
It’s something I’ve come to accept. But hey… All the colors only really exist in our brain.
For something like the opposite of that, the rainbow (plus some colors that we can’t even see) illustrated with sound, check out this Radiolab episode. Skip to around 9:30 for the action, and more fun facts than you ever knew that you needed to know about the amazing mantis shrimp.
For a long time, I’ve assumed that using “blue, indigo” in the traditional color spectrum names indicated linguistic drift. That what they used to call “blue”, we now call “cyan”, and what they used to call “indigo” we now call “blue”. That is, the primary color word “blue” has drifted away from green and toward violet. Based on what CalMeacham says on Newton being the originator of the English terms, my assumption is probably wrong.
Personally, I consider there to be six colors in the rainbow: red, yellow, green, cyan, blue, violet. “Orange” is too narrow to be useful, and “indigo” is too archaic.
Do other languages have a well-defined set of “rainbow colors”, traditional or not?
I don’t know how “well defined:” they are in other cultures or languages. The Wikipedia article in English doesn’t say, but the French edition claims that the number of colors seen varies between 3 and 9:
I’ll have to look into my copy of Boyer when I get home and see what he says.
Actually, IIRC from an earlier thread, in fact the red cone sensor in addition to primary red sensitivity has a slight sensitivity “hump” past the blue cone sensitivity, which is why we perceive violet/purple/whatever as a separate colour that appears to be a combination of blue and red.
Right. If you look at the wavelengths, the violet part of the visible spectrum should just be more blue. But very blue wavelengths also pop the red sensor some, and your brain basically imagines that the color has red in it.
It’s a bug in the system. It’s a lovely bug, though. Lovely enough to call it feature.
According to the folks in this thread (and wikipedia, where all truth is revealed!) newton went with 7 colors.
The fact that you learned ROYGBP in kindergarten is fine with me, but if I were to guess (and I am!), your teacher presented a concept that, quite frankly, is simpler to understand. It also stops 5 year olds from asking their teacher why their 8-pack of crayolas doesn’t have an “indigo” crayon, or what in the world indigo is, anyway?
I don’t know if you were bothered by my question, or I’ve been “wooshed”, but as far as I can tell, this Newton fellow decided initially that there were 5 colors, then thought about it and tried to make a connection to the musical scale and TADA! 7 colors!
Well, yes, it’s still the case that Newton said that there were seven. That’s never going to change, unless we find some lost manuscript of his. But I’m saying that most people nowadays don’t actually consider what Newton said to be official. Kindergarteners don’t know indigo. Small boxes of crayons don’t include indigo. Rainbow flags usually don’t include indigo. It looks to me like the question “When will the identification of the colors of the rainbow change” is answered perfectly well by “it already has”.
That’s an interesting question I’ve been wondering about myself. I’ve learned ROY G BIV from primary school (never heard ROYGBP myself), but when I look at online graphic (non-photographic) representations of the rainbow, I find a lot that I would call closer to ROY G CBV, with “cyan” being “blue” and “blue” being “indigo.” I wonder if there’s been some drift in the definition of cyan and blue. For example, there’s a common paint color called “cerulean blue,” which is closer, in my opinion, to cyan than it is to blue.
And what do people think of the description of “purple” vs “violet”? To me, “purple” has more of a reddish component, and “violet” has more a bluish component.
But hey… All the colors only really exist in our brain.