Impossible Teal

Only five people have seen the color "olo"

- Jacek Krywko

THE AVERAGE HUMAN EYE can see as many as 10 million variations in color, according to some estimates, from purest gray to laser green. Now scientists say they've broken out of that familiar range and into a new world of color. In a paper published in Science Advances, researchers detail how they used a precise laser setup to stimulate the retinas of five participants, making them the first humans to see an impossibly saturated bluish-green beyond our visual range.

Our retinas contain three types of lightdetecting photoreceptors, or cone cells.

S cones pick up relatively short wavelengths, which we see as blue. M cones react to medium wavelengths, which we see as green. And L cones are triggered by long wavelengths, which we see as red. These red, green and blue signals travel to the brain, where they're combined into the full-color vision we experience.

But these three cone types handle overlapping ranges of light: the light that activates M cones will also activate either Scones or L cones. "There's no light in the world that can activate only the M cone cells because if they are being activated, for sure one or both other types get activated as well," says Ren Ng, a professor of electrical engineering and computer science at the University of California, Berkeley. Ng and his research team wanted to get around that fundamental limitation, so they developed a technicolor technique they call Oz.