This content originally appeared on Envato Tuts+ Tutorials and was authored by Drew MacDonald
If the color wheel is wrong, then what colors make yellow? After all, the primary colors of red, yellow, and blue can't be made by combining any other two colors, right? As we will see, that's not always the case.
The screen you're using to read this produces yellow by mixing red and green. The primary colors depend on the color model you're using. Color theory is a fascinating and complex phenomenon deeply rooted in our biology.
It would be nice to have one color model that works in every situation, but color is more complicated than that. Instead, we have multiple models that each attempt to make color more discernible. As models, they are often imperfect and contradict each other. You can explore color theory in Laura Keung's Color Theory for Beginners and James Thomas's Advanced Color Theory: What is Color Management, or you can check out the latest color trends.
Today, I'm going to take a deep dive into advanced color theory to better examine the various illusions and optical effects of color later on in this series. Of course, any understanding of color needs to start with the eye and the brain!
Jump to content in this section:
1. Color at a physiological and psychological level
1.1 Trichromatic theory
Understanding some of the more complex aspects of color requires that we know a bit about how color works at a physiological level. The trichromatic theory was originally proposed by Thomas Young and Hermann von Helmholtz in 1802, and it has come to be the basis for most of nearly all electronic color reproduction.
Our eyes detect electromagnetic radiation, and specifically, they detect a tiny selection of wavelengths called the visible spectrum, or light. Humans are quite unusual among mammals in that we have three types of cone cells, for long, medium, and short wavelengths, whereas most mammals only have two.
This is what they mean when they say that dogs are color-blind. Compared to birds, however, we are effectively color-blind. Most birds have four different color receptors, and many species of birds can see ultraviolet light just beyond our visible spectrum.
Regardless of how many receptors an eye has, it can't sample an infinite number of wavelengths between red and blue. Each cone type is sensitive to a range of wavelengths. The short wavelength cells, for instance, can detect everything from 400 to 550 nanometers but are most sensitive to wavelengths between 420 and 440 nanometers. That roughly covers the blue spectrum of visible light.
The ranges that medium and long wavelength cells detect overlap significantly. Medium wavelength cells' sensitivity peaks between 534 and 545 nm wavelengths. Long cells are most sensitive to wavelengths between 564 and 580 nm. It's also worth noting that even for people with normal vision, the percentage of the fovea that each type makes up varies greatly from person to person.
1.2 Opponent process theory
Ewald Hering proposed the opponent process theory in 1892. Hering observed that certain colors apparently cancel each other out when mixed. For instance, a reddish green was impossible to achieve with the subtractive pigments Hering had available.
In his color model, Hering proposed primary colors of red and green as opposites and blue and yellow as opposites. James Thomas discussed this theory in greater detail in the LAB section of his article Advanced Color Theory: What is Color Management?
For a long time, it was thought that opponent-process theory was incompatible with the trichromatic theory, but we now know that primary colors have opposing secondary colors. We call those pairings complementary colors. Those pairings shift depending on the model but are a key component of many of the color illusions we experience.
2. Additive, subtractive, and structural color
2.1 Additive
Humans' physiological reliance on three wavelengths has enabled us to effectively trick the eye into seeing a whole spectrum by varying the amount of red, green, and blue light.
From James Clerk Maxwell's color image of a Scottish tartan to CRT screens to modern LED and OLED screens, red green, and blue primary colors are used to simulate millions of colors.
It is quite a bit easier to think of color in an additive model, but we are generally taught about color at an early age using subtractive models because kids have greater access to subtractive media. The more hues there are in the scene, the brighter the scene.
2.2 Subtractive
Typically, this is done with pigments that absorb everything except a specific wavelength and reflect that wavelength back to us to see. The best pigments absorb more different wavelengths and reflect a high percentage of a specific wavelength. This has an overall effect of making the scene darker as more colors are added.
If you've ever mixed too many paints together, you're probably familiar with the dark grey/brown color that results. All of the different pigments end up absorbing all of the available light and reflect nothing back for us to see. Although convenient, mixing colors from just three primaries always loses saturation and value with each additional hue added to the mixture.
Subtractive color models are intimately tied to the chemistry of the pigments used to reflect color. For instance, lead offers exceptional reflectance and durability. Lead carbonate was used to create white pigment, lead chromate was used for yellow pigment, and lead oxide was used for red pigment.
Unfortunately, lead is highly toxic, so alternatives like titanium oxide for white had to be found. However, because the purity of color is defined by the chemical properties of the pigment, toxic metals like cadmium are still widely used in artists' paints.
2.3 Structural
Structural systems are mostly seen in nature on bird feathers and insect shells, but they can also be seen in the form of rainbows and prisms, in the rainbow sheen on bubbles, and in human-made items like the security features on money.
Waves of light bend as they enter and exit transparent materials. Different wavelengths bend by slightly different amounts. This is how Isaac Newton’s prism was able to split white light into all of the different colors. It also means that structural systems can display pure hues without absorbing light and making the colors darker.
The most interesting aspect of structural color systems is how they can leverage light’s behavior as a wave. Structural systems can make hues appear even more vibrant without emitting any light themselves. It is possible for structures at the scale of light wavelengths to refract two waves in the same direction but offset by the wavelength of the light.
If the peaks and troughs of the waves align, it creates constructive interference, in which multiple waves of very specific length reinforce each other and appear more intense than any single wave was individually.
Furthermore, if the waves are out of phase and the peaks line up with the troughs, two waves of the same length will cancel each other out. Since this is all based on the angles of light refraction, the colors will appear to shift and shimmer.
3. Color models & systems
Color models are useful for reproducing specific colors without having to have a pigment or a light-emitting diode for every single wavelength. We can effectively represent the entire visible spectrum by taking advantage of the way the brain interprets color.
The spectrum of visible light is linear, from long red wavelengths to short blue wavelengths. Although they're on opposite ends of the spectrum, our brains interpret these wavelengths as being next to each other and mixing to create either magenta or violet, depending on the color model you use.
That difference between magenta and violet is one example of the limitations of color models, and you always sacrifice either value or saturation or both as more colors are mixed. In a subtractive model, the more colors you mix, the more light you subtract, so secondary colors will always be darker and less saturated than primary colors. When magenta is not a primary color, it’s necessary to mix red and blue, and you will always get a darker color, violet. In an additive system, you still lose saturation, but the color increases in brightness as more and more colors are mixed. So instead of violet, mixing red and blue in the additive RGB system gets you magenta.
3.1 CIE
| Type | Additive |
|---|---|
| Primary colors | Red, green, blue |
| Secondary colors | Cyan, magenta, yellow |
| Complementary pairs | Red & cyan, blue & yellow, green & magenta |
CIE is named for the group that performed the study, the"Commission internationale de l'éclairage" or the International Commission on Illumination. In the 1920s, CIE measured the hues that humans can perceive, and by 1931 they had developed a standard color space that covered all of the hues most humans can perceive.
They also arranged the CIE color space so that it is perceptually uniform, meaning that you can draw a line between any two hues, and the midpoint of that line will represent an exact 50% mixture of each hue. Today, the CIE color space is what other color models are measured against. James Thomas also discusses CIE XYZ in greater detail in his article Advanced Color Theory: What is Color Management?
3.2 RGB color model
| Type | Additive |
|---|---|
| Primary colors | Red, green, blue |
| Secondary colors | Cyan, magenta, yellow |
| Complementary pairs | Red & cyan, blue & yellow, green & magenta |
The RGB color model simulates millions of colors with just three primary colors: red, green, and blue. Red and blue mix to create magenta, blue and green mix to create cyan, and red and green mix to create yellow. One downside of the RGB model is that yellow being a secondary color can be unintuitive for those of us who were taught red yellow and blue as primary colors.
Hands-on experience with paint tells most of us that we can’t have a reddish green because red and green will inevitably make a brown or greyish green. In RGB though, a reddish green is yellow.
Most design now is done on RGB screens. You’re probably reading this on an RGB screen. That means that colors need to be translated when going to print since printing requires a subtractive system. Similarly, color systems like CMYK or LAB can have to be translated to RGB screen.
While RGB models cover the majority of colors available in subtractive systems, some fall out of the gamut. Ultimately, the colors you can actually see are limited to what your screen is capable of displaying. This is why color accuracy and professional monitors with expansive color capabilities are sometimes necessary.
There are multiple RGB standards. sRGB and Adobe RGB offer slightly different color gamuts. Additionally, systems like Rec. 709 and Rec. 2020 define not only color gamuts but also standards for RGB color reproduction at specific screen sizes and frame rates. All use the same three primary colors but cover slightly different gamuts.
3.3 CMYK color model
| Type | Subtractive |
|---|---|
| Primary colors | Cyan, magenta, yellow |
| Secondary colors | Red, blue, and green |
| Complementary pairs | Cyan & red, yellow & blue, magenta & green |
The CMYK color model is a subtractive model that will be familiar to designers who work with print media, as will the disappointment of seeing designs that are bright and vibrant on an RGB screen come out dull and desaturated in print.
Black is added to offset the brightness of the white substrate in dark areas of an image. Unfortunately being a subtractive model, the CMYK model is subject to the same limitations of saturation and brightness that other subtractive models have.
Designers can work around these limitations by supplementing a print with Pantone inks. The more pigments that are used to create one hue, the more light is ultimately subtracted. Using a single pigment to reflect a specific hue will result in a much brighter, more saturated color. Designers can also use effects like after-images and simultaneous and successive contrast to make colors appear more vibrant.
3.4 RYB color model
| Type | Subtractive |
|---|---|
| Primary colors | Red, yellow, blue |
| Secondary Colors | Green, orange, violet |
| Complementary pairs | Red and green, orange and blue, yellow and violet |
Red, yellow, and blue are the primary colors most of us learn about in school, and although scientifically outdated, it is still heavily employed in painting. The model traces its roots all the way back to ancient Greek philosophers like Aristotle and Plato, who linked four primary colors to the four elements as they understood them: ochre or yellow for earth, blue for the sky, green for water, and red for fire.
Franciscus Aguilonius reduced the model from four primary hues to three since green could be created by mixing yellow and blue. The model has been further refined through the centuries and advocated by artists and scientists alike, including Moses Harris, Michel Eugène Chevreul, Johannes Itten, and Josef Albers.
A major limitation of the red/yellow/blue model is that its complementary colors are mismatched in relation to what we observe. Strictly implementing the effects of opponent process color theory isn't as important in painting, but it can still make it difficult to employ illusions like after-images and to mix color precisely.
3.5 Munsell color chart
| Type | Subtractive |
|---|---|
| Primary colors | Red, yellow, green, blue, purple |
| Secondary colors | Yellow-red, green-yellow, blue-green, purple-blue, red-purple |
| Complementary pairs | Red and blue-green, yellow and purple-blue, green and red-purple, blue and yellow-red, purple and green-yellow |
Created by Albert H. Munsell in 1905, the Munsell color chart attempted to overcome the limitations of the RYB color model and provide a method for artists to accurately reproduce specific colors and incorporate the lessons of opponent process theory.
In the Munsell color circle, complementary pairs are arranged based on the observed after-image. After-image is a phenomenon we experience when the physical cone cells in the eye become fatigued and we see the opposite hue for a few seconds after stimulation has stopped.
The Munsell Color System also incorporated a 3D model of color. Multiple theorists, like Philipp Otto Runge, have attempted to chart value along a third axis in the past. Munsell's 2D color charts are arranged around a central axis. This approach separates the properties of color hue, value, and saturation and places each on a different axis in 3D space.
The Munsell color system was adopted by the United States Department of Agriculture in the 1930s. Its increased number of primaries and nomenclature has also made an appearance in proprietary color systems like Copic markers. The addition of a third axis has revolutionized color as we know it.
4. The dimensions of color: hue, saturation, and value
Breaking color down into three dimensions greatly helped artists and designers not only to communicate with each other but also to think about color and understand its illusions and effects. Designers don't have to use the Munsell system to break color down into three dimensions. In fact, if you've used the HSL color mixer in design applications, you've used this 3D model of color.
4.1 Hue definition
Hue refers to the various wavelengths of light. Primary, secondary, and tertiary colors at maximum saturation can be described as hues. Red, for instance, could be referred to as a hue, but pink and crimson could not since pink is a tint of red and crimson is a shade of red.
4.2 Saturation definition
Saturation incorporated the understanding of opponent process color theory into other models. When mixed with its complement, the color should be fully canceled out and become a chromatic grey. In models like red/yellow/blue, it was not possible to fully cancel out colors with their complements.
Red mixed with its direct complement green would become less intense but never quite fully cancel out because the actual complement of red as observed in the after-image was cyan. When the saturation of a color is changed by adding its complement, the value must also change, but the amount of value change would depend on the model. If yellow were mixed with a small amount of purple-blue in the subtractive Munsell system, the resulting yellow would have to be darker because purple-blue is a dark color.
However, if the same yellow in an additive RGB system were mixed with a small amount of blue, its direct RGB complement, the resulting grey would be as bright as the yellow itself.
4.3 Value definition
Value has also been referred to as lightness and brightness. You may have seen HSL, HSB, and HSV mixers in different applications, and the terms are generally used interchangeably.
Changing the value of a color invariably changes its saturation. When white has been added to increase brightness, the color is said to be tinted. When black has been added, it is said to be shaded. 3D color models made it much easier to see the relationship between value and saturation and communicate the difference between a bright color and an intense color.
Conclusion
Color theory has evolved a tremendous amount over the centuries, and the shift to digital displays and additive color systems over the last few decades has been one of the most significant changes.
Understanding the difference between additive and subtractive systems was never as important in history as it is today. While red, yellow, and blue sufficed in the past, that system has become outdated compared to RGB and CMYK, which are now the most widely used systems in creative industries.
Now you know more about what colors make yellow and have a better understanding of color theory. Don't forget to get up to speed on the latest color trends on the Envato blog!
This content originally appeared on Envato Tuts+ Tutorials and was authored by Drew MacDonald
Drew MacDonald | Sciencx (2024-08-13T18:46:17+00:00) Advanced color theory: Why the color wheel is wrong. Retrieved from https://www.scien.cx/2024/08/13/advanced-color-theory-why-the-color-wheel-is-wrong/
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