The Trichromatic Theory of Color Vision

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According to the trichromatic theory of color vision, also known as the Young-Helmholtz theory of color vision, there are three receptors in the retina that are responsible for the perception of color.

How Color Vision Works

One receptor is sensitive to the color green, another to the color blue, and a third to the color red. The combinations of these three colors produce all of the colors that we are capable of perceiving. Researchers suggest that people are able to distinguish between as many as seven million different colors.

Photoreceptors also tend to have different sensitivity levels. Blue receptors are the most sensitive and red the least; the ability to perceive color requires interaction between at least two types of photoreceptors. These three colors can then be combined to form any visible color in the spectrum.

Background of Trichromatic Theory

Color is a pervasive part of our visual experience. It can influence our moods, affect how we interpret things about the world, and even carry symbolic meaning. But what exactly explains our experience of color? A number of theories have emerged to explain this phenomenon, and one of the earliest and best-known was the trichromatic theory.

Renowned researchers Thomas Young and Hermann von Helmholtz contributed to the trichromatic theory of color vision. The theory began when Thomas Young proposed that color vision results from the actions of three different receptors. As early as 1802, Young suggested that the eye contained different photoreceptor cells that were sensitive to different wavelengths of light in the visible spectrum.

It was later in the mid-1800s that researcher Hermann von Helmholtz expanded upon Young's original theory and suggested that the cone receptors of the eye were either short-wavelength (blue), medium-wavelength (green), or long-wavelength (red). He also proposed that it was the strength of the signals detected by the receptor cells that determined how the brain interpreted color in the environment.

Helmholtz discovered that people with normal color vision need three wavelengths of light to create different colors through a series of experiments.

Young Helmholtz Theory

  • Helmholtz used color-matching experiments where participants would alter the amounts of three different wavelengths of light to match a test color.
  • Participants could not match the colors if they used only two wavelengths but could match any color in the spectrum if they used three.
  • The theory became known as the Young-Helmholtz theory of color vision.

Color Receptors

The identification of the three receptors responsible for color vision did not occur until more than 70 years after the proposal of the theory of trichromatic vision. Researchers discovered that cone pigments have different levels of absorption. Cones are receptors located in the retina, and they are responsible for the vision of both color and detail.

The cone receptors differ in absorption amounts due to the amount of opsin proteins in the receptor.

3 Different Cone Receptors

  • Short-wavelength cone receptors
  • Middle-wavelength cone receptors
  • Long-wavelength cone receptors

The perception of color by the brain requires input from at least two different types of cones. The brain must interpret information about both the wavelength and the intensity of the incoming stimulation. By comparing the input from each cone that has been stimulated, the brain can interpret the color of the source of that stimulation.

Trichromatic Theory and Opponent Process Theory

In the past, the trichromatic theory was often presented as competing with the opponent-process theory for dominance in explaining color vision. Today, it is believed that both theories can be used to explain how the color vision system operates and that each theory applies to a different level of the visual process.

To sum it up:

  • Opponent process theory: Color vision at the neural level
  • The trichromatic theory: Color vision at the receptor level

A Word From Verywell

Color vision and perception is a complex process that involves the eyes and brain. The trichromatic theory explains one part of this process, focusing on the photoreceptors in the eye that then send signals to the brain. Learning more about this aspect of color vision is an important part of understanding how we perceive things about the world that make up our visual experience.

2 Sources
Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Lee BB. The evolution of concepts of color visionNeurociencias. 2008;4(4):209–224.

  2. Shevell SK, Martin PR. Color opponency: tutorial. J Opt Soc Am A Opt Image Sci Vis. 2017;34(7):1099–1108. doi:10.1364/JOSAA.34.001099

Additional Reading

By Kendra Cherry
Kendra Cherry, MS, is the author of the "Everything Psychology Book (2nd Edition)" and has written thousands of articles on diverse psychology topics. Kendra holds a Master of Science degree in education from Boise State University with a primary research interest in educational psychology and a Bachelor of Science in psychology from Idaho State University with additional coursework in substance use and case management.