The Color Wheel

The color wheel is an important and widely used instrument for artists and designers. There is no "the" color wheel, or a "standard" color wheel. There are many different color wheels, serving different purposes of the following categories:

•  for mixing colors
•  for determining colors
•  for selecting colors

Definition:
A color wheel is a circular arrangement of hues, close to the order of how colors are represented in the light color spectrum.

We want to look into the process of creating a color wheel to find out more about differences of color wheels and their characteristics. We will also look into basics of color mixing. If you have water colors at hand, you can experiment and create a color wheel yourself.

Creating a Color Wheel

In the digital world the hues and their position can be calculated but more traditionally a color wheel is created step by step.

Beginning with a circle on a white/empty canvas, we then have to choose a couple of primary hues and decide on how to arrange them along the circle. More specifically we are now confronted with the following options:

•  With how many hues do we start with?
•  Which hues do we choose?
•  At which position of the circle do we put them?
   •  In what order and of which distance to each other?

If you don't limit your options to create a specific color wheel, you are free to follow your creativity or intended purpose! The decisions made at this stage make the most differences of color wheels.

1. With how many hues do we start with?

The better known color wheels are based on three primary hues but this must not be the ideal amount in every case. Especially for paint mixing purposes it can be more convenient to choose six or more primary hues to get the best result possible.

2. Which hues do we choose?

We should choose those hues which enable us best approximating the colors of the light color spectrum, i.e. the ones which allow us to mix many different hues.

Painters typically choose: Red, yellow and blue (RYB).
   (also ~ magenta red, yellow, cyan blue)
Digital imaging experts choose: Red, green and blue (RGB).
Printers typically choose: Cyan, magenta and yellow (CMY).

One characteristic of primary hues is that you can't mix them. Sometimes you simply have to take the ones available to you!

3. At which position of the circle do we put them?

Let's say we choose red as the first color to put on the circle. In terms of degrees red has a hue value of 0°. We could therefore follow the typical arrangement of degrees where 0° starts on the right hand side of a circle, or we say 0° starts at the top which is typical for a compass.

3.1. In what order and of which distance to each other?

Again we have several options for positioning the next hues. We could position them to the right or to the left of the first one and still not violate the rule of arranging the colors in accordance with the light color spectrum. In short, this determines the direction of the color wheel: clockwise or anti-clockwise.

What about the distance to each other? Typically, the primary hues are evenly spaced along the circle. This approach follows the basic rule that mixing two opposing colors of the color wheel results in a grayscale color, and the equal distance of primary hues ensures that the "right" colors are positioned opposite to each other. For certain purposes you might want to ignore this rule. This way you could shift the position of certain hues, or preserve more space for a color family respectively.

Options Summary Table:

Amount of Primary Hues	3 to 6+
Typical Hue Choices	RYB, RGB, CMY
Hue Positioning	Compass, Degrees, Individual
Hue Sequence Orientation	Clockwise or Anti-Clockwise
Primary Hues Spacing	Equal Spacing or Adjusted

Secondary Colors and Tertiary Colors

Secondary colors originate from primary colors. They are a result of mixing two primary colors of equal amounts. Secondary colors are therefore dependent on the selected primary colors. If blue (~ cyan-blue) and yellow are primary (paint) colors and mixed together, then green is a secondary color. We position secondary colors in between and with equal distance to the primary colors on the color wheel.

Tertiary colors are a result of mixing one primary and one secondary color of equal amounts. Tertiary colors therefore are also dependent on the selected primary colors. We position tertiary colors in between and with equal distance to the one primary and the one secondary color on the color wheel.

Two-Dimensional Color Wheels

The steps described this far make a basic color wheel. To enhance a basic color wheel there is the possibility of adding another color dimension to the chart. Dimensionality therefore makes another attribute differentiating color wheels.

Which color dimension can we add?
We can derive the options for a second color dimension from different color models. More specifically from color models which also have hue as one dimension determining a certain color.

Two prominent examples are lightness and saturation since they are considered the other two basic properties of color. Again the choice for either one depends on your intended purpose.

By choosing saturation you can visualize the result of mixing two complementary colors. By choosing lightness you can visualize the result of mixing hues with black and white. For the purpose of selecting colors there is another argument for choosing lightness as the second dimension of a color wheel. People are better at distinguishing differences in lightness than in hue. And, people are better at distinguishing differences in hue than in saturation. Therefore it's sensible selecting a certain color in sequence of this hierarchy.

To complete the list of options for creating a color wheel we also have to consider the radial direction of the second color dimension: outwards (~ radiation) or inwards (~ gravity).

Options Summary Table II:

Dimensionality	One- or Two-Dimensional
Second Color Dimension	Derived from Color Spaces
Radial Direction	Outwards or Inwards

Now that you know more about options for creating a color wheel, you can more precisely classify a color wheel such as the one created for the HSL Color Picker.

Color Wheel Purpose Categories

An interesting question is how we can distinguish color wheels according to their purpose? Maybe we can find answers for this question by analyzing the benefits for a user of the respective instrument.

1. Color Mixing

Paint is not available in every color an artist wants to apply. It also wouldn't be economical to buy that many. This means a painter, for example, must get along with the available paints and try to find ratios of mixture for desired colors. To find these ratios of mixture a painter must experiment because paints have different attributes. You can imagine it's not desirable for an artist to experiment while working on a creation because this would interrupt the flow of creativity.

It's more convenient to do a study in advance and a color wheel can be used as a template for this study. By approximating hues of the light color spectrum you can find ratios of mixture for many colors. A painter can then refer to these insights while working on a creation. The benefit of a color wheel used for color mixing is that the position of hues and their distance to each other visualizes ratios of mixture.

Moreover, the logic behind such a color wheel also works the other way around. By remembering the position of just a few hues you're able to guess what color is behind an arbitrary position. For example, if red is positioned at 0° and yellow is positioned at 60°, you can easily guess what color is behind the position of 30°. On a side note, this is the benefit you get from using HSL color values in HTML documents. You save time by not having to look up what color is behind a hexadecimal color code.

2. Determining Colors

Several industries are confronted with the challenge of finding out the color values of a color sample. First and foremost, to reproduce a certain perceptual experience but also to find out how well two samples match, or how distinct two samples are from each other. One way of finding the color values of a color sample is to compare the color sample with a set of well defined colors, picking the best matching color of the set and then looking up its color values.

Picking the best matching color is not as easy as it may sound though. The difficulty is largely dependent on the design of the illustrated comparison set. Difficulty in this context means how confident someone can decide whether a color of the comparison set is a match or not (yes or no) and which one of two colors of the comparison set is a better match (better or worse). A balanced amount of colors in a comparison set is one requirement to increase confidence.

Another factor is how each illustrated color dimension is segmented. For determining colors it has been found best practice to segment color dimensions by equal perceptual differences. A color wheel designed accordingly, in conclusion, illustrates a comparison set of colors through which you can determine colors with greater confidence and then look up the respective color values of your sample.

3. Selecting Colors

What is a "good", the "right", or a "beautiful" color for a specific workpiece? This is a tough question to answer, especially when you - theoretically - have 16.7 million colors to choose from. Moreover, choosing a color is usually not only about one color on its own but also about choosing the "right" color in context with other colors.

Several principles and theories have been developed to simplify the task of selecting colors. Color wheels are frequently used for both explaining and applying these principles and theories.

A "suitable" color wheel for selecting colors is an instrument which supports the application of principles and theories by which the outcome of a color selection is perceived aesthetically appealing. You may find this not being true for color wheels designed for the purposes of mixing or determining colors.