I understand that this is light theory and that it works, as well as how it works, but it seems like I was taught in elementary school that the three primary colors in life are Red, Yellow and Blue… was I taught wrong or was my art teacher smoking too much weed to get it right or what?
The primary colours of light are red, green and blue because you add them together to make the combinations; paint pigments, on the other hand, are subtractive - they work by absorbing light and reflecting only some of it back; the subtractive primaries are actually cyan, magenta and yellow.
The three colour receptors in your eye are red, green and blue. Your TV or monitor mixes light of these primary colours to produce any colour in the visible spectrum. Well, almost. But mixing light is an additive process; mixing paint is subtractive, and for pigments the primary colours are magneta, yellow and cyan.
In theory you could reproduce any colour with magenta, yellow and cyan (plus black) on a white background, but in practice the fancier printing processes use even more colours to compensate for the limitations of the available primary pigments.
Red, yellow and blue were what were known as primary pigments. I have no idea what use they are.
Since mixing red, yellow and blue paint results in brown (and not black) in my experience, and that red, green and blue light results in white (as you can see if you play with the colour- convergence on your monitor). I’m still baffled about the r/y/b theory.
Again, it should be cyan, yellow and magenta, but in primary school education, red and blue are close enough to magenta and cyan to be good enough.
It took a long time for color theory to get it right. The r-y-b “primaries” idea was developed a couple hundred years ago, but is too imprecise. Magenta is sort of red, & cyan is one of the range of colors called blue (I think Newton called our additive blue “indigo”), but the words “red” & “blue” each cover a broad range.
Properly, the additive primaries (“rgb”) & subtractive primaries (“cmy”) alternate evenly. But the cultural terms for colors are older, vaguer, & more arbitrary, so “cyan” & “blue” are both “blue” to most English speakers.
red, as used in television
yellow
green
cyan, or “printer’s blue”
blue, as used in television
magenta, or “printer’s red”
I have discovered, to my horror, that even some high school college art teachers seem unaware of the differences.
Then there’s my graphic artist uncle, who said once that he wished colors didn’t have names… 
No, I think it was, “we should never have named colors.” Maybe he had a point.
I once posted a similar thread which led to no solid conclusions. The real puzzle is how the primary colors of light are demonstrated at many science museums by using three spotlights using colored filters (or colored cellophane) to produce the primary colors of light…and one is free to “mix” the spotlights of colors on a white screen.
Yet, these colored filters are made in no different way than, say, colored crayons. And. when I look through yellow and blue cellophane filters, I see green…which is what the primary colors of color would have pedicted, but not what the primary colors of light would have predicted.
So, when do primary colors of light manifest their “true colors”, so to say???
- Jinx
Yes they are; they’re transmissive; a red gel lets red light through; a blue gel lets blue light through and a green one lets green light through; add these three colours of light together in one place and they add up to white.
A red crayon absorbs everything except red light; a green crayon absorbs everything except green; mix just these two on paper and you have a problem - the green crayon reflects green but absorbs red and blue, the red one reflects red but absorbs green and blue and the blue one reflects blue but absorbs green and red, so somewhere along the line, all of the colours are getting absorbed; you get (theoretically) black.
Actually, you can achieve the same kind of effect if you stack the coloured gels together - the red light admitted by the red gel is absorbed by the green and blue ones, and so on; you get a (theoretically) opaque black gel.
I vagely remember some kind of graphic displaying red, green, blue, yellow, cyan, and magenta as faces on a cube.
here it is.
I’ve known many lighting geeks who refer to colors only by their Rosco number.
“The logo is supposed to be in Conestoga and Morning Fire! And that wall! That’s not Peaceful Melody with Soft Dew trim!!”
Your uncle would really hate the current state of affairs in the paint industry.
So RGB is the right way and RYB is actually CMYK - interesting. Thanks guys!
Well, I’m going to have to disagree that RYB is “actually” CMYK. CMYK is the subtractive 4-color process that produces the largest color gamut. RYB is a perfectly valid set of primaries when mixing pigments, it just produces a smaller gamut than you can achieve with a CMYK subtractive process.
Indeed. Yellow plus blue really does make green, just like your kindergarten teacher taught you.
You can get a “gamut” or range of colors by mixing together many combinations of colors of lights, and also combinations of colors of pigments. To get a gamut that includes all the colors people can perceive, you actually have to mix together physically impossible or imaginary colors of light such as the X, Y and Z used by the cie (you might think of these as red, green and blue with more than 100% spectral purity, because for example mixing X with white light can make 100% spectrally pure red light). Imaginary or not, they are perfectly valid for all the mathematical treatments of color science. But you can get a pretty nice gamut if you mix red and blue and a nice spectrally pure green of about 515 nm. In practice it is typically the green that does the worst job of being pure and having the right wavelength to maximize the gamut.
In theory you can get all the colors you want with ideal pigments of cyan, magenta and yellow - you don’t need black. The black is typically the first additional pigment that is added to make up for the deficiencies of available real physical pigments. That is, it’s like Fridgemagnet says, only worse.
Mixing lights is technically beautiful, a straightforward linear method based on the by-wavelength spectral sensitivity curves of our three color receptors. Mixing pigments, on the other hand, is surprisingly mathematically complicated. Avoiding metamerism makes it all the harder.