Can you see "forbidden colors"?

Try to imagine a reddish green color, not a brown that can be obtained by mechanical mixing, but a color that resembles red and green at the same time. Or try to imagine a yellowish blue, not green, which results from mixing, but a yellowish blue.

Is it difficult for you to imagine something like that? The reason for this is that despite the existence of such flowers, you have probably never seen them. Red-green and yellow-blue are the so-called "forbidden colors". They consist of a pair of shades, the light frequencies of which compensate each other in the eyes of a person, which is why they cannot be seen at the same time.

How do we perceive colors? Retinal cells, called "neuronal opponents", light up when we see red. This burst of activity tells the brain that it is red that we are seeing. The same opponents of neurons are suppressed in green. Yellow activates them, while blue suppresses them. Most colors cause a mixture of effects among both groups of neurons that our brains can decode. However, red cancels green, and yellow cancels blue, which is why we can never perceive both of these colors at the same time, coming from a single source.

Rather, almost never. As the scientists explain, in order to see these colors, you just need to know where to look.

The color revolution began in 1983 when the work of Hewitt Crane, a leading visual scientist, and his colleague Thomas Piantanid appeared in Science magazine. Titled "Seeing Red-Green and Yellow-Blue, " the work spoke of the ability to see "forbidden" colors. Scientists have created images in which green and red, and in the other blue and yellow stripes "ran" one after the other. They showed the images to volunteers using an eye tracker that clearly records them at the level of a person's eyes. This ensured that the light from each strip of each color affected the same retinal cells. For example, some cells have always perceived only red, while others only perceived green.

Participants in this visual experiment said they saw how smoothly the borders between colors disappeared, two colors turned into one. Incredibly, experts were able to redirect the retinal cells, while people saw colors that they had never encountered before!

The authors wrote in their work that each of the participants in the experiment called the color they saw "simultaneously red and green." Some respondents, despite the fact that they knew what colors they were looking at, could not name what they see in one word, or even describe the color. And this despite the fact that one of the participants in the experiment was an artist with a large "color vocabulary".

With blue and yellow colors, the experiment gave a similar result.

The research of Crane and Piantanide made the scientific community ponder, but few turned to the results obtained by scientists. Further research only confirmed the initial findings, suggesting that when viewed correctly, forbidden colors can be seen.

In 2006, Po Chang Se, a specialist at Dartmouth College, and his colleagues set out to repeat the 1983 experiment, slightly modifying it. Participants were now presented with a color map on a computer screen, and they had to use it to match the color they were shown. And they showed them those same variable stripes, a color that people in the 1983 experiment could not describe.

The result was that people saw a mixture of two colors (for example, yellow and blue), but not forbidden colors. Then, when, in the next stage of the experiment, the boundaries between yellow and blue dissolved, and the colors absorbed each other, the participants found this color on the color map without any problems: it turned out to be dirty brown.

And if the resulting color is a dirty brown, why couldn't the participants in the 1983 experiment be able to describe it? "There are an infinite number of intermediate colors, so it is not surprising that we sometimes lack the vocabulary to describe them. However, just because a color has no name, one cannot say that this color is forbidden and that it not in color space ".

However, later it was still proved that forbidden colors exist. Xie's experiment was criticized for not using retinal stabilization.

Scientists are still trying to define a clear mechanism that allows people to see forbidden colors. You will never be able to contemplate them in nature or in the color wheel, but perhaps someday someone will invent a portable device with a built-in eye tracker that will allow us to easily see forbidden colors.