Purple is not violet.
Where is purple on the spectrum?
Bah. Took too long editing my post:
Purple is not violet. Violet is a set of wavelengths near the lower limit that our eyes can perceive that are not absorbed by our corneas. Purple is, as you note, the addition of red and blue. While there are metamers of violet that can be made from red and blue wavelengths, they are not violet. The reason that they can be made to look alike is due to the chemical composition of our eyes’ cones and the multiplexing that our nerves do to the signals from those cones.
Purple is not on the spectrum.
So two colors can look alike but still be different colors? I thought the defining quality of a color was what it looked like. There are lots of different ways to make something appear blue, but as far as I can tell we don’t distinguish between them as long as they are the same shade of blue.
Perfect then. As I was saying, what you see is only partly related to the spectrum of colors. After all, according to what you beleive, we can actually see colors that don’t exist on the spectrum at all.
I still say that purple isn’t violet but exists at a shorter wavelength than blue. Whatever, you can see that the conclusion is the same.
Yes. That is why televisions can reproduce a scene of arbitrary colors with only 3 colors. It’s not actually reproducing the color of someone’s shirt, it’s producing a red, blue, and green light whose actual brightness, when absorbed by rods in your eyes, approximates the absorbtion that your eye would have done from the light that bounced off of that shirt.
You can say it all you want, it doesn’t make it true. Purple is bimodal; it’s not a simple range of wavelengths. It is a set of wavelengths that are around blue together with a set of wavelengths around red. There are no wavelengths in the set that are shorter than any wavelength of the original blue that you made it from.
You do realize that ROYGBIV is just a mnemonic device right?
And an accurate one. Indigo is the spectral color you were thinking of, not purple.
they only called it indigo to make the mnemonic device work.
Anyway, it’s been a long time since I’ve seen a display technology seminar, but if people are interested in understanding the technicalities of color perhaps they should begin by understanding color spaces.
The only point I mean to make is that what we see is only partly related to the spectrum our eyes receive. Our eyes make really bad spectrometers.
Uh, that’s our point too: we can see purple, but it’s not on the spectrum. So, I’m not sure what you’re trying to argue.
Q.E.D. - I don’t know why you think we were on opposite sides. Someplace along the line I thought I was actually defending something you said.
Really though, my chemistry teacher did tell me that the only reason we called it indigo was to make the mnemonic device work. But then chemists aren’t known for coordinating colors.
I don’t, but I also understand that purple is a mixture of two spectral colors (red and blue) and not a spectral color itself. Indigo and purple are not the same thing. However, that’s the sum total of the disagreement I have with you.
Yes that was what I was defending.
Most folks agree that indigo was shoehorned in, but not to maintain the mnemonic device of some ficticious gentleman’s name. (Cite)
Can you not make indigo from red and blue? Those color space diagrams seem to indicate that you can.
OK I see
I was using the general term.
Water isn’t a gas… it’s a gas or a liquid or a solid, depending on pressure and temperature (it actually has several solid forms)
You know, most people take the “basic” form of water to be the liquid, and the others to be the “variants” 
Oh, and yes, you can have such things as gold vapor (gold in gas form), but you have to go to such extreme conditions to get any considerable amounts of it that we need to invite the physicists in so they can start arguing about whether it’s gas or plasma.
(Christopher, Chem Eng spec Orgo, MS in Theo Chem - there have been compounds detected in plasma and something doesn’t need to be a compound to be a chemical)
Obviously the definition of chemical is a little bit arbitrary. It is interesting to know that some presumably ionized compounds can exist in a plasma. I dissagree with the assertion that everything is a chemical.