How Impossible Colors Work

How to See Impossible Colors

When teams of researchers tried to re-create Crane and Piantanida's revolutionary experiments with impossible colors, they often came up with disappointing results. Instead of seeing brand-new hues of greenish-red or blueish-yellow, subjects most frequently described the blended color as mud-brown [source: Wolchover]. Others would see fields of green with pixelated red dots scattered across it. Impossible colors became a scientific joke.

But in 2010, impossible colors were back in the headlines. This time, a pair of visual researchers from the Wright-Patterson Air Force Base in Ohio, believed they had determined why Crane and Piantanida had succeeded where others had failed.

In a Scientific American article, biophysicists Vincent Billock and Brian Tsou identified the combination of eye tracking and luminance (brightness) as key to tricking the brain into seeing impossible colors [source: Billock and Tsou].

Billock and Tsou ran their own experiments in which subjects were again strapped to a chinrest and monitored by the latest retinal tracking technology. With the images stabilized to the subjects' eye movements, Billock and Tsou played with the brightness or luminance of the two opposing color stripes.

If there was a difference in brightness, the subjects experienced the pixelated colors reported in earlier experiments. But if the two colors were equiluminant — exactly the same brightness — then six out of seven observers saw impossible colors [source: Billock and Tsou]. Even better, two of them could see the new colors in their minds for hours after the experiment was over.

Author's Note: How Impossible Colors Work

Let's take a moment to appreciate the miracle that is color vision. The animal kingdom has evolved the biological technology to detect subtle variations in the energy wavelengths of reflected light and translate that data into 3-D color images. It's estimated that humans can see as many as 10 million different colors. Why in the heck did we evolve this ability; so Crayola could release a 10 million pack of crayons? Some evolutionary biologists believe trichromate color vision evolved in primates to help us spot colorful berries. Other animals have eyes and brains that can see beyond the visible spectrum. Honeybees can see in infrared. Butterflies and some fish perceive ultraviolet light. The existence of impossible colors makes you wonder what else is out there that we can't see ... yet.

Related Articles


  • Billock, Vincent A.; Tsou, Brian H. "'Impossible' Colors: See Hues That Don't Exist." Scientific American. February 2010 (May 30, 2015)
  • Nassau, Kurt. "Colour." Encyclopaedia Britannica (May 30, 2015)
  • Pantone. "How Do We See Color?" (May 30, 2015)
  • Wilkins, Alasdair. "Train Yourself to See Impossible Colors." io9. Dec. 9, 2010 (May 30, 2015)
  • Wolchover, Natalie. "Red-Green & Blue-Yellow: The Stunning Colors You Can't See." Live Science. Jan. 17, 2012 (May 30, 2015)