Try to imagine, if you will, a reddish green shade— not the dull brown you get when you mix the two pigments together, but rather a color that is somewhat like red and somewhat like green. Or, instead, try to picture yellowish blue — not green, but a hue similar to both yellow and blue. If your brain is drawing a blank, don't feel bad. Even though those colors do exist, they cannot be seen by the human eye. Composed of pairs of hues whose light frequencies automatically cancel each other out in the human eye, they're supposed to be impossible to see simultaneously. They are called "impossible colors" and the reason you can't see them is something called opponent process.
The human eye has three cone cells that register color that "work in an antagonistic fashion": Blue vs. yellow; Red vs green; Light vs dark. There is an overlap of wavelengths of light covered by the cone cells in the human eye so you see more than just blue, yellow, green. White, for example, is not a wavelength of light. The human eye does, however, perceive it as a mixture of different spectral colors. "Because of the opponent process, you can't see both blue and yellow at the same time, nor red and green. These combinations are so-called impossible colors."
What's interesting is that there is an argument against the existence of impossible colors. Some researchers believe that these so-called impossible colors; yellowish-blue, and reddish-green are really just intermediate colors. "While chimerical colors are well-documented imaginary colors, the possibility of impossible colors remains disputed."
Is there a way to see these impossible colors? Maybe yes and maybe no. Impossible colors like reddish green and yellowish blue are tricky to see. "To try to see these colors, put a yellow object and blue object right next to each other and cross your eyes so that the two objects overlap. The same procedure works for green and red. The overlapping region may appear to be a mix of the two colors (i.e., green for blue and yellow, brown for red and green), a field of dots of the component colors, or an unfamiliar color that is both red/green or yellow/blue at once!" It's a little difficult for frogs to cross our eyes, I can tell you that. But I did try it and all I can is...I'm dizzy!
You won't see these colors in nature or on a color wheel but one day, perhaps, someone will discover a handheld impossible color viewer with a built-in eye tracker that will enable humans to see these amazing and indescribably glorious colors. And when you see them, it'll be like seeing purple for the first time; an amazing and breathtaking experience.
I hope you'll stop back by tomorrow for a look at the December Calendar of Special Days. December is about a whole lot more than just Christmas and New Year's Eve!