Art Fundamentals No 1: Color Theory

I fully admit I have no formal training in art. I certainly appreciate that this is not some declaration of any innate talent; but, more that it is an acknowledgement that I have a great deficit in knowledge that impairs my ability to improve my skills.  Ask any artist and you are likely to get a variety of responses to “the fundamentals” albeit they tend to center around shape, form, values, anatomy, and color theory.  And its this latter one, color theory, that I want to spend a bit of time sharing what I’ve learned thus far, along with provide a bunch of resources (mostly online) that I think are worthy of further exploration.

It should be noted that while I am generally trying to get a practical understanding of color theory, inevitably there is a bit of a rabbit hole for which one can find one’s self going down.  While I personally find the deeper parts on the philosophy of color exceedingly important to build a strong mental model on the theory, arguably you do not need these underpinnings from a purely practical perspective on application.

Perception Trumps Physics

One of the most important things to appreciate in understanding color as an artist is that color is not absolute, but relative.  This is especially important to note for those with a science or physics background, such as myself, who may fall prey to thinking of color as purely a manifestation of wavelength of light.  While this is certainly true in context to the emission and absorption of electro-magnetic radiation, this level of understanding, if anything, largely obstructs us from better understanding how the human eye is stimulated by light that is then processed by our brains.  In this regard, the philosophy of color is more central to our pursuits than the science of light.  Like I said, the rabbit hole is never far, and once one stumbles into it it’s hard not to fall very deep indeed.

A generally accepted, albeit incorrect understanding of human vision, is that we see in three colors of blue, green, and red.  And that the brain processes this to create the infinite number of colors that we perceive.  While it is correct we have three types of cones, unfortunately, their labels oversimplify the reality.  These three types of cones actually perceive a spectrum of colors that largely overlap; but where they differ is where they are most sensitive within the color spectrum.  Interestingly, blue cones are the least common and do not exist inside the fovea centralis where both green and red cones are crammed.  It is important to note, again, that the cones are colloquially labeled for a single hue (or color), but in reality they are sensitive to very large spectral range with a significant overlap, especially for the red and green cones.  For the persnickety reader, these cones of red, green, and blue are often referred to as L, M, and S, respectively, by the academic literature, where the letters are references to the long, medium and short wavelengths of visible light.

Now, we do not actually know how we perceive color, although they are of course theories such as the opponent processing theory which generally states that the signals from the 3 cones L, M, and S along with rods (brightness) are used to compute three differences, or: 1) quantity or brightness which is a combination of all cones and rods ; 2) amount of red-green; 3) amount of blue-yellow.   This theory handily explains why humans cannot perceive a yellowish-blue or a greenish-red, since in opponent processing theory these colors work into opposition to each other to create a single value, as it were, that is used to process color.

It is particularly important to remember that for any given wavelength of the EM spectrum it does not have, as an intrinsic quality, color.  Color is fundamentally a quality of human perception.  Human perception of color works through a subtractive process noted above by the opponent processing theory, so whereas a physical understanding of light (not color) is arranged as a linear spectrum with longer wavelengths such as “red” to one side, and shorter wavelengths such as “blue” on the other end, the human perception of color is better modeled as a circular spectrum where colors are next to their neighbors in a harmonious, blended manner with complimentary colors always opposite to each other.

Color Wheels

The concept, generally speaking, behind a color wheel is that you can start with the three primary colors – in the case of above we show red, yellow and blue – and subsequently add them in varying proportions to get other colors on the wheel.  In the above, if we combine blue and yellow we get green.  And blue and red produce purple.  And so on and so forth.  Note, the above color wheel greatly simplifies matters as its ignores variations of saturation and value.

Relationship of Hue, Chroma and Value

While we often think of “red” as a color, it is more accurate to consider “red” a component of color.  More specifically, color is generally accepted to be broken into three major attributes, or

1. hue – the family of color such as red, blue, yellow, et cetera
2. chroma – the intensity or saturation of the color
3. value – the amount of lightness, or white or absence thereof

Why is this important?  While a color wheel is a very practical tool, it occludes from an artist the importance of value, and more in particular, how not all hues are created equal in this regard to value.  This is where Munsell color system can provide some insights, even if we opt to not adopt the nomenclature proposed by Munsell.

Munsell’s color system helps to take those three above attributes, and depicts them in three dimensions.  Munsell is not the first to connect these three attributes into three dimensional space, but he is the one who best pursued this to create a system that most closely matches what the human eye can perceive.

One might think of these 3 attributes defining a sphere, or an apple, since along the central core going top to bottom is are the values.  In Munsell color system, everything was meant to have well defined values such that any color can be accurately described by its coordinates in this three-dimensional space.  Looking from the top down on this core working radially around are the hues such as red, yellow-red, yellow, green-yellow, et cetera.  Finally, working outward from the core along any defined hue is the chroma, or intensity of the hue for a given value.  While both hue and value are constrained between a range, chroma is not.  In theory, chroma extends out to infinity.

Now, while that is all very interesting, the real insight comes from the fact that the sphere is not a smooth sphere at all.  The below is a vertical slice of the Munsell sphere between hue 5Y (yellow) and 5PB (purple-blue).  What I want you to pay particular attention to is how the for any given value, the amount of chroma (intensity of color) varies for both hues.  I would argue that the most intense purple-blue happens around chroma of 12 and value of 5.  But for the yellow, it s actually at chroma of 10 and value of 8.  Why is this important?   This is critically important, especially if as an artist you start with values to block in shape and form first, and then use overlays of color.  Because the values you pick will implicitly determine what colors you can subsequently overlay.

	12	10	8	6	4	2	0	2	4	6	8	10	12
10							255 255 255
9						228 228 250	232 232 232	243 227 207	250 227 178
8					190 201 239	200 200 222	203 203 203	215 200 181	221 200 154	227 200 126	233 199 97	237 199 63
7			142 176 241	154 175 225	164 175 210	173 174 195	179 179 179	188 173 155	194 173 128	200 173 101	205 172 72	210 172 29
6	79 150 244	101 150 227	116 149 213	128 149 198	138 148 182	146 148 168	150 150 150	161 147 129	167 147 103	173 146 75	178 146 42
5	46 124 214	72 123 199	89 123 185	101 123 171	111 122 156	120 122 142	124 124 124	134 121 103	141 121 77	146 120 48	150 119 9
4		38 97 172	59 97 158	74 97 144	85 96 130	93 96 116	97 97 97	108 96 77	114 95 52	119 94 25
3			26 72 133	45 72 120	58 72 106	67 72 92	70 70 70	81 71 55	87 70 33
2				20 49 93	35 49 79	44 49 66	48 48 48	57 48 34	63 47 6
1	5PB		13 28 56	23 28 45	28 28 28	37 27 9			5Y
0							0 0 0

This is well illustrated by Sycra with one of his YouTube videos where he clearly demonstrates how the process of value to color is interlinked.  To wit, it is critically important to understand this relationship otherwise your application of colors will result in muddied, muted colors or otherwise otherworldly colors that do not land well.

Primary and Secondary Colors

There is nothing specifically special about primary colors.  Well, there is, but that is only when you are trying to increase the number of unique colors that can be perceived, but we will discuss this in a bit under gamut.

The concept of primary colors, and in particular, the three primary colors that we are taught of red, green, and blue (RGB) are purely an artifact of the study  of human perception and those three cones (L, M, S) we mentioned previously.  We will ignore additive vs subtractive process differences for now, but just note that colors are added together when combining light such as your monitor, but colors are subtracted when other mediums such as printing and painting are involved.  That said, the primary colors of RGB are for additive processes, whereas CMYK (cyan, magenta, yellow, and black) are for subtractive processes.

That all said, the combination of the primary colors create secondary colors which are purely defined as colors created when two of the primary colors are combined in equal proportions.  And the combination of the primary and all subsequent colors effectively result in those primary color’s color gamut.

Complimentary Colors

Complimentary colors are simply colors that are on opposite sides of each other in a color wheel.  Generally speaking, at least for the RGB color wheel, complimentary colors have the largest perceived contrast to each other.  Thus, one can argue orange is used for outdoor where as it provides the greatest contrast against greens and blues such as trees, skies and water.  And more so, complimentary colors are aesetically pleasing to the majority of humans.  Whenever considering your color scheme for a picture, one simple approach is to big one color to be the primary color, and its compliment to be the second color.

Color Gamut

But what is a color gamut?  Simply put, it is the color space or all the color combinations that can produced by combining colors first starting with the primary colors.

Again, as we emphasized above, color itself is purely a quality of the human brain’s ability to perceive different combinations of light with differing wavelengths and intensity.  Color itself is not a quality of the light itself.  So this why we say that there is nothing particular special about the primary colors in and of themselves.  They are selected for a singular purpose: to produce as many possible permutations of color that the eye can perceive.  If you selected three different colors arbitrarily you’d be able to create a color wheel, but you would discover that some of the colors from the RGB color wheel just could not be reproduce.

So RGB are our primary colors for the sole reason that they yield the largest color space, or color gamut, tuned specifically to the human eye.  Pick a different set of primary colors and you get a different gamut.  And this, folks, is why when working digitally it is so important to know your color space.  Since different color spaces do not entirely map onto each other; colors that can be represented in one gamut simply do not exist in another gamut.  This is particularly acute when transitioning from display color space, which is typically RGB, to print’s, which is nominally CMYK.

Note how different color gamuts only generally overlap.  In particular, whereas RGB has the largest gamut albeit still not sufficient to reproduce all the colors that the human eye can perceive, it is significantly better than print such CMYK.  Given how much smaller CMYK is to RGB, it is very important when creating artwork that will be printed to understand this and ensure that you work within the correct color gamut for the intended output, otherwise you will sorely disappointed in your results; this no more so than when comparing the differences of your artwork on your computer screen to its output on a printer.