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From what I've read, theoretically all colours can be mixed to a higher level of saturation when done using a CYM pallete, especially for magentas and hot pinks. Is this true? Can a limited palette of just these three colours and white suffice for painting?

2 Answers 2

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Cyan, magenta and yellow are actually the primary colors you should use when painting with inks and paints.

(I'm surprised we didn't have this kind of question asked before, because most of us are taught the wrong primary colors in school and by paint manufacturers)

Fair warning: the information in the following section is WRONG but it's what most people learn about the color wheel.

The typical color wheel that is printed in (some) art books and on paint boxes looks sike this:

enter image description here

The primary colors are: red, blue and yellow.

Every child learns that:

  • Mixing red and green yields brown
  • Mixing red and blue yields purple
  • Mixing blue and yellow yields green

But have a closer look. The wheel is not uniform and yellow has a much bigger area than all other colors. The color right next to red is magenta, which is actually lighter than the two colors it's supposed to be mixed of. And anyone who ever tried mixing a vibrant purple from red and blue was disappointed by the muddy outcome.

How it actually works

There are actually 2 sets of primary colors and both of them are correct, but they apply to different ways of mixing color.

White light is a composition of every visible color. If you shine a red light at a spot, then add a blue light and finally a green light, the center where all colors add up, is white. This is called additive color. This applies to all TV, phone or computer displays and anywhere where color is made by mixing light.

If you mix red, blue and green paint on a paper, you end up with (at least almost) black, though. Your paints don't work the same way as light. You need to take color away (subtract from the mix) to end up with white. This is called subtractive color. This applies to all printers, pens, inks and paints and anywhere where color is made by mixing substances.

The primary colors of additive mixing are: red, green, blue. (RGB)
The primary colors of subtractive mixing are: cyan, magenta, yellow. (CYM or CYMK)

The primary school art class colors red, blue and yellow aren't even a valid set of primary colors!

color wheels
(Image source and more detailed information)

And here is another example of CYM color wheel that displays how adjacting colors mix:

Can only 3 colors suffice?

Unless you use high quality inks, the answer is still: no.

The color wheel is an idealized model based on wave lengths of visible light. We can manufacture color filters that absorb all but a single wave length (color) and mix colors additively in a perfect way. But as far as I know there are no pigments that reflect only a single wave length, which means that there is no paint of a perfect primary color.

The chemical and physical composition of pigments and the binders and additional ingredients in paints influence how the paints look when mixed. Linseed oil, for example, has a slightly yellow tint, which always influences the oil paints it's mixed with.

Many paints, especially cheaper ones, already contain a mix of different pigments. They may look like a primary color to your eyes, but they physically react different than a pure primary color pigment when being mixed.

Most yellows, for example, contain chalk or white pigment to make it more opaque without adding more of the expensive yellow pigment. You'll never get a rich, lush green by mixing a cheap yellow paint with blue.

(Side note: that's why the ink for inkjet printers is so obscenely expensive. I dare say that inkjet printing is the closest we've ever come to perfect subtractive color mixing, and it still isn't perfect at all. A printer has to use very pure, high quality ink to be able to mix all colors. And even then you need an additional black ink cartridge because the mix of all 3 primary colors doesn't yield a perfect, opaque black.)

In addition to that, it's simply more convenient to have certain colors premixed, because it can be very tricky hitting just the right hue when mixing a color from just the primary colors.

And lastly, it can be a matter of cost. Especially brown mineral pigments like Umber and certain chemical pigments are cheap to manufacture in high quality, so mixing the same hue from more expensive primary colors is a waste of resources.

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  • Thanks for your answer, just a one thing I wanted to clarify. You said that in real life it would likely not work due to the additives used, but I would only plan on using single pigment paints, so I'm wondering if that would still apply. My thinking is that I would still use a mostly standard palette for the majority of my painting, but I would reserve a high quality magenta and cyan for producing maximally saturated colours. Plus, would all of this still work for other subtractive colour mixing, like for pencils or watercolour? Thanks
    – user9526
    Aug 17, 2020 at 2:16
  • @user9526 Keep in mind that the color wheel is an idealized model based on wavelengths of visible light. There are still aditives like acryllic medium, oil or other binders in single pigment colors and they do influence the color of the paint. The most vibrant paints are usually the ones bought with a (not primary color) pigment. Inks are the purest painting medium with the least additives and react the most like color theory teaches us. And yes, this works for all subtractive mixing, although it's much harder to mix pencils and they have more additives in their lead.
    – Elmy
    Aug 17, 2020 at 4:15
  • As someone trying to develop a CMY watercolor palette, the other real life restriction is what colors of paint are manufactured. From what I've read there isn't an agreed-upon standard pigment for any of the three colors. Yellow and magenta choices seem often to be a matter of taste, but cyan seems more like how well you can approximate the correct color by what's available.
    – Reve
    Aug 17, 2020 at 16:24
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    "The primary school art class colors red, blue and yellow aren't even a valid set of primary colors!" Actually, I would say that red-blue-yellow is the ONLY practical set of primary colors, given the limitations of the real world. All the color theory in the world doesn't change the fact that 99.9999% of the time, mixing magenta paint with yellow paint will result in orange-ish paint, not red. (Although of course, mixing blue paint and yellow paint probably won't get you the nice grass green you wanted, either, which is why they make so many different colors of paint.)
    – Martha
    Aug 17, 2020 at 21:05
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Are there any downsides when painting with a cyan-magenta-yellow palette instead of the traditional yellow-blue and-red?

If you start with red, yellow, and blue as the building block pigment colors, you can often come close to most of the other colors you may need, but there will be color holes and inaccuracies. That's because you can't create the primary subtractive colors of magenta or cyan, and red and blue contain the baggage of color components that may not be components of the color you want to create.

Take magenta as an example. Magenta looks like it could be created from red and blue (and is actually a mix of red and blue light). With subtractive color, red is a combination of magenta and yellow, and blue is a combination of magenta and cyan. So mixing red and blue is equivalent to mixing magenta, yellow, and cyan, with a higher proportion of magenta.

That is equivalent to a mix of magenta and black (the CMYK model). If you were to add white to offset the black, it would be a mixture of magenta and grey. You can't get to pure magenta starting with red and blue because they already contain other colors that you can't remove.

So CMY is required to accurately reproduce the full range of colors if you need them. But there's a tradeoff. It is hard to produce some colors well by combining CMY primary colors. That's especially true trying to create primary colors of the "opposite" RGB color space. Combining primary colors tends to produce a muddier or less intense color than starting with a dedicated colorant of the desired color. That's why high-end inkjet photo printers usually include one or more RGB primary colors with the CMY mix.


Can a limited palette of just these three colours [CMY] and white suffice for painting?

Let me start by saying that you would probably want to add black to that mix. Combining CMY pigments is imperfect, producing a dark, muddy gray rather than jet black. That's why all but the cheapest color inkjet printers add black ink to the mix.

Whether this pallet will suffice depends on your requirements, but you would probably find it inadequate if you want intense, vibrant colors. The reason becomes clear if you look at how subtractive color works.

The RGB and CMYK color spaces are shown in the image below (note that the colors aren't "to scale"; they are more of an abstraction because the full gamut of color can't be reproduced in the diagram):

enter image description here courtesy: Summit Printing

It is often described that there are colors represented in RGB that can't be represented in CMY. That's inaccurate. The difference is in the nature of emitted color vs. reflected color, which those models represent.

The CMY and RGB primary colors are "opposites". Cyan is what's left if you remove red from white light (so it's just green and blue light). Magenta is what's left if you remove green from white light (so it's just red and blue light). Yellow is what's left if you remove blue from white light (so it's just red and green light). On the color wheel, the primary colors for CMY fall between the RGB primary colors, and on the opposite side of the wheel.

The RGB primary colors are the hardest to reproduce in CMY because they are subject to the most degradation. Reflected colors work by absorbing the light wavelengths of other colors. You see magenta because green light is absorbed more than the other colors. You see cyan because red light is absorbed more than the other colors. If you are limited to CMY primary colors, you produce blue by combining magenta and cyan, and you see blue because that's the light color that's left.

But what's left isn't pure blue in real life. There's some green reflected by the cyan and some red reflected by the magenta, the absorption of other colors isn't 100%, and the blue isn't 100% reflected. You can't reflect as pure or as bright a blue as you can emit from a blue light. But at least when you start with a blue pigment, you eliminate some of those degradations.

So if you limit yourself to the CMY primary colors (assuming they were the precise colors), it would limit your ability to create some colors well.

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