Scientists Discovered a New Color. It’s Been Right in Front of Us All Along.

The human eye perceives color using three types of cones, but no natural light can stimulate just the the cones associated with medium-wavelength light in the visible spectrum.
A new tool, nicknamed Oz, can do just that by mapping the retina and specifically stimulating only these medium cones and no others.
The result, according to the authors, is a new color (which they’ve named “olo”) that’s kind of like a deeply saturated blue-green, but unlike any color a human has ever glimpsed before.

The human eye is a wonder of evolution, and is our primary window into understanding the known universe that surrounds us. But even despite the hundreds of millions of years that fashioned our irises, formed our retinas, and molded our light-sensitive photoreceptors, our eyes can only see a fraction of the electromagnetic wonders that criss-cross the cosmos.

And even in this small visible sliver of the electromagnetic pie, some colors remain hidden from our view—until now. In a new paper published in the journal Science Advances, scientists from the University of California Berkeley and the University of Washington describe how they managed to only stimulate the cones in our eyes responsible for interpreting medium wavelength light using laser light. The result was a never-before-seen color.

“The ultimate goal is to provide programmable control over every photoreceptor [light-sensing cell] in the retina,” Fong told Live Science. “Although this has not been achieved to that level, the method we present in the current study demonstrates that a lot of the key principles are possible in practice.”

First, a brief refresher on some elementary biology. The human eye senses light and color thanks to the millions of rods and cones located in the retina. While rods handle low-light conditions and enable dark vision, cones are responsible for bright light and color, and typically come in three flavors: long (L), medium (M), and short-wavelength (S) cones. When mapped to the wavelengths in the visible spectrum, this roughly amounts to L cones interpreting the color red, S cones glimpsing blue, and M cones falling in the middle near an approximation of the color green. (Some people, known as tetrachromats, actually have a fourth rod that sensitive to orange, but that’s a story for another time).

Because M cones sit in the middle of the visible spectrum, they mostly overlap with L and S cones, meaning there’s no natural light that stimulates M cones exclusively. So, researchers developed a tool—nicknamed Oz for Frank L. Baum’s The Wizard of Oz—that mapped a person’s retina, isolated the M cones, and then used a laser to specifically stimulate only those middle-of-the-road cones. The result, according to the researchers, was a color that was a type of blue-green no human had ever seen. The team nicknamed the color “olo,” which is a reference to a 3D map of color coded in binary 0,1,0 with “1” indicating the full stimulation of the M cone.

“Attempting to activate M cones exclusively is shown to elicit a color beyond the natural human gamut, formally measured with color matching by human subjects,” the authors write in the paper. “They describe the color as blue-green of unprecedented saturation.”

Although some scientists remain unconvinced that “olo” is indeed a new color—one vision scientist told The Guardian that the work has “limited value”—Fong and his team hope that further exploration of the retina using Oz could help treat color blindness and other retinal diseases, including retinitis pigmentosa. The tool could also be used to simulate what it would be like to be one of those genetically mutated women (it’s mostly women) that have four distinct cones and can see millions more colors than the average human.

For as much as we think we know when it comes to color, evidently there’s more than meets the eye.

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