Basically what the title asks.
All the other colors of the rainbow are either primary or secondary. Violet is a shade of purple and (as I’ve always understood it) indigo is somewhere between navy and purple.
In: Other
I think you just ‘outed’ yourself as not having kids.
As a parent I can tell you they combined indigo and violet into purple at least around a decade ago. I’m not sure how ‘wide spread’ this is at all, but it’s definitely ‘a thing’.
IIRC the Indigo and Violet thing came from ‘7’ being a special number in Western / Judeo-Christian beliefs (aka “7th Heaven”, etc.) and they stretched purple into indigo and violet so that we’d have 7 colors as well.
EDIT – I think people were confused by my response – what I was trying to say is that in my area we’ve removed “indigo” and “violet” from the rainbow and “purple” is taught in their place. I was being a bit light hearted in my response in saying if you had little kids you’d have known this because it was definitely a thing my parent-group, like WTF? we have to learn a new rainbow now?
Purple doesn’t actually exist on the visible light spectrum at all—it’s made up by our minds. Violet does actually exist on the light spectrum.
Purple is what your brain perceives when both the red and the blue cones are stimulated. Violet and indigo are colors you perceive, the difference is that you can see light of a single wavelength and perceive indigo or violet, but you can’t see a single wavelength and perceive purple.
Now, the red cone does have a small amount of sensitivity at those short wavelengths, but not enough that a single wavelength can look halfway between red and blue.
As for combining indigo and violet, sure, you can, but you don’t have to. There’s a smooth and continuous transition between the colors of the rainbow, it’s a bit arbitrary where you draw lines, and how many lines you draw.
In my country it is a color of the rainbow. 7 colors: Red, Orange, Yellow, Green, Blue, Indigo, Purple
Here’s a bit of detail about indigo as a color:
https://handwovenmagazine.com/what-is-indigo/
Basically, Isaac Newton more or less arbitrarily decided on seven as a magic number–not necessarily due to religious reasons, but that 7 is a common number in other uses (the musical scale, for example). Indigo was far, far more popular of a color during his time (it was a common dye) so the distinction made a lot more sense back then.
We didn’t always have a separate name for some colors like orange and purple. That’s why “roses are red, violets are blue”. When they were naming the colors of the rainbow, they described the higher-energy “blue” as being the color of a violet.
It’s all kind of arbitrary anyway, the rainbow is a continuous spectrum of wavelengths, it’s only our eyes and our brain that compartmentalize it into a handful of distinct basic colors
It’s cultural courtesy of Isaac Newton, who took the infinite spread of colors from a prism and assigned them seven names, seven being an auspicious number. He could have omitted orange or added cyan just as easily. For purposes of the color spectrum indigo and violet are both pure colors with a single wavelength. Artistically you are correct, they are both mixtures of red and blue.
Nature blurs the line a bit with rainbows, which typically have a very faint secondary rainbow just inside the primary. You might not even see it, but the brightest bit of the secondary (red) overlaps with the blue of the primary and makes it look a little purpleish, even as the rest of the secondary fades to nearly invisible.
“Purple” isn’t a wavelength of light. It’s a *harmonic*.
We have specialized cells in our eyes to detect light with peaks at certain wavelengths (color), but only 3 colors:
– red
– green
– blue
As you can see, there is no violet detector. We detect “in between” colors like yellow being in between green and red when both sets of red and green cells are stimulated.
Red is light with a space between its peaks of at most about 750 nanometers. At the other end of spectrum of what we detect is blue at about 450 nm at the shortest.
If you know much about music, a harmonic is when you can fit two waves in the space of one. This means that there would be a peak in the larger number range every two periods.
Violet is about 380 nm. 380 x 2 ≈ 750 — so it sets off the red detector **and** the nearby 450 nm blue detector.
Since we usually see these 2 receptor colors as “in between” the primary colors, we perceive it as a mix of red and blue as though they somehow mixed to make a color way outside their wavelength. But they don’t. We call that imaginary mix of red and blue purple.
Because it isn’t. When you look at visible light, there is no wavelength that corresponds to what we call “purple”. Our brains make it up, because different “sensors” in our eyes are being stimulated by a combination of other wavelengths. Violet light exists, it’s the light towards the very end of the visible spectrum beyond 380nm. You can choose to name it “Vurple” and the one you call purple something else, but that’s immaterial.
Like all man made classifications, it’s an arbitrary choice. Color is a spectrum, not a 7-step scale
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