In addition to being an element of design, color is also an entire body of theory called, not surprisingly, color theoryIt may seem odd to think about color as theoretical, but you have to understand this in the context of scientific pursuits going back at least to the middle ages with the publication of Kitāb al-Manāẓir (Book of Optics, 1021ce) by Arab scholar Ibn al-Haytham (Alhazen to us Westerners...). In this book, Alhazen laid out many discoveries about the nature of light and vision that we take for granted today, e.g. that light does not originate from the viewer's eye, then bounces off an object, and that it is, in fact, the other way around.

An image from Alhazen's "Book of Optics"
Alhazen remained the authority on light and color perception until Sir Isaac Newton's Opticks, wherein he essentially proved that colors are components of white light, sending aloft the first systematic volley in a massive discussion of color that has spanned continents, encompasses a multitude of definitions, concepts, systems, and design applications - enough to fill several hundred encyclopedias – and it even continues even to this dayColor theory is concerned primarily with the properties of different wavelengths of light and how we perceive them. But it's also focused on the interaction of colors, i.e. how different combinations of colors can cause colors to change in the appearance of the constituent colors. However, there are three basic categories of color theory that are logical and useful in practical application: the color wheel, color harmony, and color relativity. 

The Color Wheel


Three color wheels - Harris, Today, Goethe

A color circle, based on red, yellow, and blue, is traditional in the field of art. Sir Isaac Newton developed the first circular diagram of colors in 1666. Since then, scientists and artists have studied and designed numerous variations of this concept. Differences of opinion about the validity of one format over another continue to provoke debate. In reality, any color circle or color wheel which presents a logically arranged sequence of pure hues has merit. Let's arbitrarily start with the work of Bauhaus artist and educator Johannes Itten and his 1961 piece entitled Farbkreis, a German word that translates literally to "color circle."

Johannes Itten, "Farbkreis," 1961
This piece reflects a more painterly understanding of colors — unsurprising, as Itten was himself a painter (in addition to a weaver). The classic primaries red, yellow, and blue are considered so because they cannot be made by mixing other pigment colors.

For painters and other types of artists and designers who manually mix pigments, Itten's system works well. But contemporary color theory is really more concerned with frequency interaction between differing hues, and how to represent colors accurately with different types of technology. These technologies fall into two distinct categories - screen-based and print-based - and the various colors systems used in each couldn't be more different.

Contemporary color wheel; Color systems; Color types
GDPE diagrams color systems 33Additive color systems arise from the direct mixture of different wavelengths (colors) of light. The primary colors in an additive system are generally red, green, and blue. Laptops, desktops, smartphones, tablets, televisions, portable gaming systems, smartwatches...basically anything with a color screen combine, or add, red, green, and blue-colored light in various combinations to generate about 90% of the colors you and I can see. Combining all of these primaries in equal parts will generate white light. A system like this is specifically called an RGB system (see below). Therefore, any design work meant to be viewed on a device of some kind - e.g. broadcast graphics, video, app assets, website imagery, etc - should be created in an RGB system or mode.

GDPE diagrams color systems 32Subtractive color systems arise from the filtering of light. The most common primary colors used in a system like this are cyan, magenta, and yellow. Generally, you will find this color system in the four-color printing process, where a black 'channel' or 'key' is used to register or align the other three colors together. As the alignment key, black is generally shorted to K, and the entire system labeled CMYK.

In the case of CMYK, the pigments placed upon (usually) white paper act as filters, absorbing or subtracting wavelengths of light other than those corresponding to the colors we perceive. This is why systems such as these are called subtractive: light is filtered or subtracted when colors are generated. 

Anything kind of digital work that is meant for print should be made in the CMYK space. 


Color Schemes

There is no right or wrong way to mix colors, as acculturation and personal preferences play a large role in what we find acceptable. However, basic color schemes that use the modern color wheel can be very useful in discovering universally acceptable color combinations. Below are the six geometrically derived color schemes, and respective examples of palettes obtained from them: 

Color schemes derived from the color wheel 

 Color Harmony

Harmony can be defined as a pleasing arrangement of parts, whether it be music, poetry, color, or even an ice cream sundae.

In visual experiences, harmony is something that is pleasing to the eye. It engages the viewer and it creates an inner sense of order, a balance in the visual experience. When something is not harmonious, it's either boring or chaotic. At one extreme is a visual experience that is so bland that the viewer is not engaged. The human brain will reject under-stimulating information. At the other extreme is a visual experience that is so overdone, so chaotic that the viewer can't stand to look at it. The human brain rejects what it can not organize, what it can not understand. The visual task requires that we present a logical structure. Color harmony delivers visual interest and a sense of order.

In summary, extreme unity leads to under-stimulation, extreme complexity leads to over-stimulation. Harmony is a dynamic equilibrium.

Some Formulas for Color Harmony

There are many theories for harmony. The following illustrations and descriptions present some basic formulas.

1. A color scheme based on analogous colors

ctheory leaf 

Analogous colors are any three colors that are side by side on a 12 part color wheel, such as yellow-green, yellow, and yellow-orange. Usually one of the three colors predominates.

2. A color scheme based on complementary colors

ctheory orchid  

Complementary colors are any two colors that are directly opposite each other, such as red and green and red-purple, and yellow-green. In the illustration above, there are several variations of yellow-green in the leaves and several variations of red-purple in the orchid. These opposing colors create maximum contrast and maximum stability.

3. A color scheme based on nature

cteory nature

Nature provides a perfect departure point for color harmony. In the illustration above, red yellow, and green create a harmonious design, regardless of whether this combination fits into a technical formula for color harmony.

Color Scheme Generators

  • is a very simple and straightforward color scheme generator, and it has a pretty slamming iOS app as well! I use this all the time.
  • provides a really excellent color scheme generator. Let's check it out!
  • allows you to create a theme from an existing image. Very cool.
  • And finally, the generator Adobe would have you use,

Color Relativity

How color behaves in relation to other colors and shapes is a complex area of color theory. Compare the contrast effects of different color backgrounds for the same lavender square. A washed-out lavender appears more brilliant against a black background and somewhat duller against the white background. In contrast with orange, the lavender appears grayish; in contrast with blue-green, it exhibits brilliance. Notice that the lavender square appears a little larger on black than on the other background colors.

Different readings of the same color
I know this is bizarre, but that's the same dull lavender (#988ea6) across the four different backgrounds.
In the image below, the same lavender color is used as one background for a sort of dull blue. The same dull blue appears on a more saturated cyan background as well. The result appears to be two different foreground colors, but I assure you, they are the same dull blue on either side. 
Though the exact same color, the less saturated blue squares look different depending on their background. 

Observing the effects colors have on each other is the starting point for understanding the relativity of color. The relationship of values, saturation, and the warmth or coolness of respective hues can cause noticeable differences in our perception of color.

One of the first Western artists to formally experiment with color as it is perceived was Eugene Delacroix, who was much more concerned with the actual wavelengths hitting the retinas than the colors are rational brains told us we were looking at. The 2-minute video discusses Delacroix's then-unique approach to color, and how it led directly to the earliest developments of the Modern Art movement:

Stemming directly from the work of artists like Delacroix, the Impressionists raised the exploration of light and color to an entirely new level. A pejorative term at the time, the early Impressionist artists initially called themselves the Anonymous Society of Painters, Sculptors, Engravers. They were later labeled Impressionists due to the inclusion of Claude Monet's seminal landscape entitled Impression, Sunrise

Claude Monet, "Impression, Sunrise" (1872)

In the painting above, Monet was attempting to record colors and their interactions the way he perceived them, as opposed to rendering the actual colors found in each constituent piece. The result is a hazy grayish blue, resulting from the interaction of two complementary colors: orange and blue. Another result: the sun appears to glow right off the canvas due to its interaction with the surrounding blue. Monet has employed painterly techniques known at least since Delacroix, but rather than try to simply record the event, as any photograph would do, Monetpoetically used color and form to highlight his perception and memory of the event.