The opponent-process theory was proposed in 1982 by German physiologist Edwald Hering. In his theory he explains that our ability to perceive color is under the control of three opposing systems which are generated by the three different photoreceptor cells found in the retina of the human eye.
Each of these photoreceptors – or cone cells – are sensitive to particular light wavelengths:
- Short frequency
- Medium frequency
- Long frequency
Each of these wavelengths have opposing pairs:
- white and black,
- blue and yellow
- red and green
The three color pairs also have three specific chemicals, and each causes two types of chemical reaction:
- An anabolic process
- A catabolic process
With the anabolic process one member pair is stimulated through a build up process. With the catabolic process, the other member of the pair is going through a destructive process. These pairs basically oppose each other, act antagonistically, and cancel each other out. This means that a red-green receptor cannot transmit chemicals for both colors at the same time.
Opposing pairs can also be observed when running an experiment and looking for a longer period of time at a specific color such as red (creating a positive/excitatory response). When closing our eyes our brain generated a so-called “after image” but we will perceive the opponent color green (creating a negative/inhibitory response). These responses are controlled by so-called opponent-neurone. These are neurons which have an excitatory response to some wavelengths and an inhibitory response to wavelengths in the opponent part of the spectrum.
With these insights we can deduce that strong opponent colors should not be used adjacent to each other, or within the same region of a graphical display where its important to distinguish function and meaning as readers will have to put in more effort to distinguish the pair at first.