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Practical Color Theory

or Art School Lied

INTRODUCTION

      Much of color theory taught in art school (and high school, and in art books...) is wrong.

      That is a little bit of an overstatement. Most of it isn't incorrect so much as it is incomplete, could be done better, or is just not very useful. And we're talking basic information. The color wheel? Primary colors? Dinosaurs, but ones who live on due to a sort of intellectual inbreeding. My hope is that some of these have started to change since I left art school, but I haven't seen any signs to indicate that it is happening. The result is many students who leave with a very poor understanding of how to properly mix colors.
      So if, like me, were taught the color wheel and the red-blue-yellow primary color scheme, please read on. Hopefully you will leave with a more useful understanding of how color works (and, as a result, how to mix the colors you want).

Color Basics: What Art School Got Right

      Art school did teach the dimensions of color correctly, and I need to cover it now. The principles and terminology covered here are important to understanding what follows.
      Every color can be expressed in three dimensions- hue, saturation and value: (refer to Fig. 1 for help)

  • Hue is what we traditionally think of as "color", meaning where a color is along the outside of the traditional color wheel. Red, blue, or yellowish-green, for example.

  • Saturation is how intense or pure the color is. A pure yellow, for example, is said to have high saturation. A yellow that is almost gray, conversely, is said to have very low saturation. (Remember though that because both colors in that example start from the same yellow, they both are of the same hue.) An easy way to think of saturation is how gray a color is.

  • Value is how light or dark a color is. This dimension, as you can guess, goes from white to black. A tint is created by adding white, and a shade is created by adding black. You can, of course, add both black and white at the same time, but the effect will be to desaturate the color. Whether you create a tint or a shade in that case will depend on whether the net effect creates a lighter or darker color than the original hue.
COLOR IN THREE DIMENSIONS

Fig.1 The three dimensions of color
What's Wrong With the Color Wheel?

      The color wheel, as seen in Fig. 2 to the left, was developed by Sir Isaac Newton based on the newly developed optical spectrum. A prism, he found, split light into a rainbow. Newton wrapped the rainbow around into a circle and labeled the colors. It is, in essence, the same color wheel in use today.
   Unfortunately a wheel is a poor choice for a practical understanding of color mixing. A graphic representation should be visually meaningful, and the color wheel simply isn't. A wheel implies that all of the colors are created equal when, at the risk of sounding prejudiced, they simply aren't.
      Since Newton, we have developed the concept of primary colors. We will get back to the sticky issue of primary colors farther down, but for now you simply need to understand primary colors in the way they are taught in art school- they are a set of colors (usually three) A) from which you can mix all of the other colors, and B) which cannot, themselves, be created by mixing other colors. In other words, not all colors are created equal.
      "As everyone knows", blue and yellow make green and blue and red make purple. The layout of the wheel would imply, therefore, that purple and green make blue. They don't.
      Secondary colors are the colors made by mixing two primaries. If you assume that red, blue and yellow are the primary colors, then green, purple and orange are the secondary colors.

THE COLOR WHEEL

Fig.2 The Newtonian color wheel
The color Triangle: A Better Model

      A better model is the color triangle, as shown in Fig. 3. It conveys all of the information of the original color wheel, but it also communicates extra information such as the relationship of primary colors to secondary colors and vice versa.
      If you now draw a straight line between two colors, the midpoint is a close approximation of the color you would get if you mixed those two colors in paint. For example, the midpoint between blue and yellow is green. The midpoint between green and purple is a VERY desaturated blue. If you have mixed paints much before, that should sound familiar.

Complimentary Colors: A Powerful Tool

      Another slice of color theory that art school got right is the concept of complimentary colors. Complimentary colors are ones found on opposite sides of the color triangle (or color wheel) from each other. Blue and orange, red and green, or greenish-yellow and reddish-purple, for example. The best way to desaturate a color is to mix it with its compliment. A curious thing happens when you don't mix them however. When you use compliments next to one another, they cause each other to appear more intense. When you look at paintings in the future, pay attention to how many are based on a blue/orange color scheme. Or red/green or yellow/purple. Brown is essentially a desaturated orange, so blue/brown is the same as blue/orange.

A COLOR TRIANGLE

Fig.3 A triangular form of the original color wheel
Art School's Dark, Dirty Secret

      All of that is just a lead-up to art school's big secret: red, blue and yellow are not primary colors.
      Once you have been snookered into believing this one big untruth, it is too easy for you to think that all of the other color problems you have are your fault, not the underlying paradigm's. And they get you early. They teach you at a young age that blue and yellow make green. We all know it, and everyone keeps repeating it, so it must be true, right?
      But artists learn early that if they want a really pretty green, they won't get it by mixing blue and yellow. What you get is a dirty, muddy greenish color, not a truly vibrant green. A really pretty purple can't be found by mixing red and blue. You can get a very nice orange by mixing a pure yellow and a pure red, but we will see why in a moment.
And the scary fact is that printers have known the truth for decades.
Cyan, Magenta and Yellow

      Cyan, magenta and yellow are much closer to being true primary colors. This revelation brings with it some truly astounding points. Astounding, that is, if you have come to believe in the red/yellow/blue primary set (as I once did).
      To begin with, you can mix blue and red. Try it. Get some true cyan and magenta and mix them by adding a little magenta to a larger amount of cyan. If the cyan and magenta are pure, you should get a very pretty blue. It feels like you have suddenly become an alchemist, toying with the very fundamental properties of nature. I just mixed blue! you may think to yourself.
      Cyan is often described as a greenish blue color. That is like describing blue as "greenish purple." In truth, blue is actually a reddish cyan. Similarly, magenta looks like a purplish red when it is actually the opposite; red and purple are derivatives of magenta.
      Look at Fig. 4, what I have called the "Real Color Triangle." I have labeled (approximately) where blue and red fall on this new scheme. I have also added an inner triangle connecting blue, red and yellow, representing the "traditional color wheel" colors, or those you can actually mix under the old set of primary colors.
      Take notice of the color at the midpoint between blue and yellow. It isn't green; it's a dirty, grayish green... like you get when you mix blue and yellow on your palette. The same applies to purple. It should now be clear why you don't get a clean, vibrant green when you mix blue and yellow. If you are working with red, blue and yellow, green lies outside the possible range of mixable colors!

THE REAL COLOR TRIANGLE

Fig.4 A color triangle based on cyan, magenta and yellow
      Orange, as you can see, still lies between red and yellow. It is no wonder that you could mix a saturated orange even under the old primary color scheme.
      Another point to notice is that even if you turn the inner triangle into a 5-sided shape that includes purple and green, you are left with colors outside the shape. Without cyan and magenta, you are losing color range.
      Cyan, magenta and yellow are not perfect primary colors. I have read that it is possible to mix cyan from colors just to either side of it. Cyan will also make a perfect gray from colors both the left and the right of its compliment when in a perfect world only one color would mix with cyan to make a perfect gray. As printers know, working with cyan, magenta and yellow is better than working with red, blue and yellow but it still has limitations. They still do not fit a Platonic ideal of primary colors. In fact, no colors do. There are not true primary colors. But cyan, magenta and yellow seem to be the best we have figured out so far.
      I have a fellow artist friend who, after learning about cyan, magenta and yellow, moved almost strictly to painting with them. He uses those three colors, white, black, and a few browns that could be mixed but would be inconvenient to do so. The colors in his paintings have become richer than before.
      So that is the end of my advice on color theory, right? No, not at all. There is another concept having to do with how to create rich, pleasing tints and shades. This is something my art school never even touched on. It has to do with the spectrum and how our eyes perceive color.

The Color Solid

      A man by the name of Munsell once tried to create what you could call a 3-dimensional color wheel- a solid sphere which displayed all of the colors AND their various shades and tints and, within the form, the various levels of saturation of all of the surface colors. In essence, the sphere would represent all possible colors.
      Munsell hit upon several problems with the idea. He started with a sphere because as colors tint towards white and shade towards black, the number of different colors our eye can perceive decreases. But how many shades and tints we could discriminate between was not the same for different hues. In fact, the values of the saturated, untouched hues themselves were not equal. Yellow is a very light color, and accordingly our eyes can better discern small differences on the yellow side of the light hemisphere. Similarly, red is a dark color and blue even darker. As colors get blacker, we lose the ability to see much difference between shades of yellow but can see plenty of reds and even more blues.

THE COLOR SOLID

Fig.5 Munsell's color solid (or color top)
      To address these issues, Munsell made two changes to his colors solid. Instead of simply placing the pure colors around the center, he moved them up or down to their correct value (Fig. 6). For example, pure yellow is a light color, so it moved higher in the solid. Secondly, Munsell made the solid bulge in places in which our eyes can perceive a greater range of colors. The yellow area bulges on the light side and the red and blue areas bulge in the dark hemisphere. The result is Fig. 5.
      A two-dimensional display of the values of the various hues can be seen in Fig. 7, below.

RELATIVE LIGHTNESS OF COLORS

Fig.7 This graphic shows the relative values of the color range, with white circles (usually) indicating the pure hues
PURE HUES IN THE SOLID

Fig.6 This graphic shows the pure colors in regards to where they appear in Munsell's color solid
     What does all of that have to do with how you paint? Well, it illustrates that colors don't move in a straight line as they get lighter or darker. The most dramatic example is yellow. What happens when you add black to yellow? The resulting color is not a nice, dark yellow. Instead, it looks greenish.
     As most objects get lighter, they will bend towards yellow. After all, that is the color your eye can perceive the best in the light range. This is particularly true of green and red objects. If you lighten red by simply adding white, you will end up with a pink color. Most people think that "pink" is the same as "light red", but most red objects in the real world don't look bubble-gum pink in the lighter areas. What is the difference? A true "light red" as seen on a real-world object has small amounts of yellow. The hue doesn't stay red as it moves toward white, but bends toward orange.
     Remember, this is an effect of how we perceive colors, not a property inherent to the color. The diagram in Fig. 8 roughly shows the perceived movement of several colors as they get lighter or darker. Red bends towards orange as it gets light, but stays red (perhaps moving to magenta) as it gets dark.
     Like red, green bends toward yellow, but more dramatically. A light green is often almost a greenish yellow. Green objects in the real world that don't bend towards yellow as they get lighter (like certain plants) stand out as different. Green, being the most mobile of colors, moves toward blue just as quickly as it gets darker.
     Blue, on the other hand, is pretty close to directly opposite from yellow in the cyan/magenta/yellow color triangle, so it should not come as a surprise that blue does not gravitate to yellow as it gets light. Instead, blue moves toward the tonally lighter cyan on its way to white. Like red, blue sometimes moves toward purple as it gets darker, but not always.

PERCEIVED COLOR MOVEMENT

Fig.8 Perceived movement of colors as they get lighter or darker
SUMMARY

To summarize the key points:

  • A color has three dimensions- its hue, saturation and value.
  • The most effective primary colors are cyan, magenta and yellow. Blue and red are mixable colors within this scheme.
  • Imagine colors in a color triangle instead of a color wheel. Using this model, color mixing can be approximated much more easily simply by using straight lines between points on the triangle.
  • Use complimentary colors- beside one another to make colors appear more vibrant, and mixed together to make desaturated colors.
  • An object's perceived color changes hue as it gets lighter or darker, in most cases becoming more yellow as it lightens and more blue or red as it darkens.
While this issue has gone more into a practical color theory than most art schools, it is far from complete and skims over a lot of detail, history and science. It presents only one model out of several and ignores finer complexities. It also does not go into the difference between mixing of light, which works different from the mixing of pigments. In short, it is meant to be a useful introduction to color theory as an artist should understand it. Several of the graphics used on this page were borrowed from Bruce MacEvoy's "Handprint: Color Vision" website. Visit his site for a much more comprehensive, in-depth, well-researched discussion of color in all its facets.


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This document last updated Mon Oct 2 11:00:31 2006.