14 DAY TRIAL // Our perception of colors – while pretty good on some occasions – is entirely lacking on others. Researchers highlight two so-called “forbidden colors” that our eyes cannot see due to the very nature of how we perceive colors.
The colors are reddish green and yellowish blue. Just to make matters clear, we are not talking about the colors you get when you mix red and green, and yellow and blue, respectively. When mixed, the first pair results in a dull brown, while the second one gives you a certain shade of green.
The fact is that our eyes cannot perceive a color that is both red and green, or yellow and blue, at the same time. This happens because the wavelengths at which these colors can be found in the spectrum cancel each other out extremely well inside the eye.
Researchers say that this is what makes these two color combinations nearly impossible to see at the same time. The key to understanding how our eyes work when perceiving red and green lies in cells called opponent neurons, located on our retinas, LiveScience reports.
When we see red, these neurons enter a frantic state of electrical activity, which is translated inside the visual cortex as this particular color. A lack of activity in these nerve cells means that we are seeing green. Therefore, the two colors are mutually exclusive, as far as the brain is concerned.
A different set of opponent neurons is similarly in charge of detecting yellow light, and activate themselves when this happens. But blue light inhibits activity in this neural subgroup, making these two colors mutually exclusive as well.
Most colors we see in our daily lives contain a mixture of these four hues inside them, but they can be decoded by the opponent neurons. However, the wavelengths of pure red cancel out those of pure green completely. A similar thing happens between blue and yellow.
But scientists say that these forbidden colors can indeed be seen. Back in 1983, leading visual scientists Hewitt Crane and Thomas Piantanida published a paper describing an experiment in which adjacent strips of green and red, and blue and yellow, were presented to test volunteers.
By using an eye tracker, the team was able to ensure that each color entered a different group of opponent neurons. Participants reported seeing the borders between the two colors gradually fade away, as they blurred into each other. This allowed them to see the forbidden colors.