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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?

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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 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 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 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 at 21:05
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TL;DR

  • It isn't necessary or advantageous to build your pallet on CMY colors based on paint being subtractive color.
  • Using only CMY colors will be a disadvantage compared to RYB because you won't be able to create as big a range of mixed colors, and some mixed colors won't be as vibrant.

The Details

Are there any downsides when painting with a cyan-magenta-yellow palette instead of the traditional yellow-blue and-red?

It's important to distinguish between additive/subtractive color, the color space, and the color pallet. Those are conflated within the question.

  • Additive vs. Subtractive Color: Additive color is how the color of emitted light works. Subtractive color is how the color of light reflected off colored surfaces works.

    All the colors of emitted light add together to create white. With light reflected off a colored surface, combining all of the colors approaches black. Paint is subtractive color, so you can't produce white by combining colors.

    "Additive" vs. "subtractive" describes how colors interact, and whether combinations of colors get lighter or darker. It's the "mechanics" of color, but it doesn't define what colors you can create.

  • A "color space" is a theoretical model for representing a working portion of the color spectrum mathematically. It's a tool to create a large range of colors based on a few building block components, which can be primary colors.

    The Red-Green-Blue model is a good representation of additive color (red, green, and blue being the additive primary colors). The Cyan-Magenta-Yellow model is a good representation of subtractive color, those being the subtractive primary colors.

    Neither the RGB nor CMY color spaces can represent the full range of colors in the visible spectrum, but they are usually adequate for practical purposes. Color printers normally have CMY primary colors that they use to create a range of millions of mixed colors.

    Note that RGB and CMY are not the only color spaces that have been defined. There are many systems for defining colors in terms of some basic color components. It also isn't necessary to use primary colors to create a new color, even within a given color model.

  • The color pallet is the collection of colors you will use to mix and create other colors. Paint isn't typically made at the precise CMY primary colors that would allow you to accurately create every other color from just those.

    For that matter, painting isn't typically based on creating all colors from just primary colors. But to accurately reproduce every color in a color space using only its primary colors, those colors must be precise.

    Note that when using a medium with subtractive color, like paint, RGB won't work; that only works when combining colored light. You can't make yellow by combining RGB pigments. But you can start with red, yellow, and blue as the building block pigment colors.

    Paint manufacturing takes advantage of very rich colorants as the starting point, and those colors aren't the precise primary colors. You can get to the same range of mixed colors by starting with a pallet of colors other than the primary colors of a particular color space, it may just take starting with more than three colors.

So to your title question, there's no reason to limit yourself to a pallet of primary colors, either RYB or CMY, and neither is better for this purpose simply because paint color is subtractive.

Independent of the color space, you can mix paint to produce other colors. Red and yellow will produce orange, blue and yellow will produce green, and red and blue will produce purple, even though paint works via subtractive color. In these examples, you're producing colors by starting with a secondary color for one or both components rather than all primary colors.

That said, it is hard to produce some colors with a vibrant quality by combining primary (or secondary) colors, especially creating primary colors of the "opposite" color space. For example, high-end inkjet photo printers often include red and/or blue ink with the CMY mix because it is hard to create intense red or blue by mixing CMY colors. Combining primary colors tends to produce a muddier or less intense color than starting with a dedicated colorant of the desired color.

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. Beyond what's described above, there's another consideration: CMY represents a smaller color space than RGB, and RGB can't represent the entire visible color spectrum (there are colors represented in RGB that can't be represented in CMY; that's part of the reason why it's hard to create intense red or blue from CMY primary colors).

So if you limit yourself to the CMY primary colors (assuming they were the precise colors), it would limit your ability to create some of the colors you could create if you started with RGB (or RYB). The RGB and CMYK color spaces are shown in this image (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

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