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Researchers at UC Berkeley used a specialized retinal-stimulation system to make five people perceive “olo,” an unusually saturated blue-green. Their 2025 study found that the tested percept extended beyond the natural human color gamut under the experiment’s conditions. That is a striking result—but olo is not a newly discovered wavelength or a paint color, and an image on a screen cannot reproduce it.
What is olo?
Olo is the name researchers gave to a percept produced by selectively stimulating a class of retinal cells called middle-wavelength-sensitive, or M, cones. The five participants described it as a blue-green with unprecedented saturation. Berkeley coverage compared it with teal, peacock green and the “greenest green”; these are verbal approximations, not swatches of the actual percept.
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The distinction matters for painters: a pigment reflects light, and a display emits light. Both rely on ordinary light reaching the eye. Olo arose from an unusual signal delivered directly to selected photoreceptors, so neither paint nor a screen can reproduce the experiment.
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1Fix the driver behind crashes, sound loss and screen glitches2Clear out junk files and repair common Windows errors3Scan for outdated or missing drivers - takes under a minuteHow did scientists create olo?
The team’s prototype, called Oz, combines retinal imaging, eye-motion tracking and targeted laser microdoses. It maps the locations and types of cones, then aims stimulation at chosen cells while accounting for eye movement. The study describes targeting thousands of spectrally classified cones in a small retinal field. Berkeley’s institutional summary describes the platform as controlling up to 1,000 photoreceptors at once; those are different descriptions from different sources, not a consumer-device specification.
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In ordinary vision, cone responses overlap. Natural light that stimulates an M cone also stimulates neighboring long-wavelength-sensitive (L) and/or short-wavelength-sensitive (S) cones. As UC Berkeley optometry professor Austin Roorda put it, “There’s no light in nature that can only stimulate the M-cones.” Oz attempted to bypass that constraint by delivering microdoses to mapped M cones. The idealized percept from pure M-cone activation is the researchers’ theoretical target; the prototype only partially expanded color space toward it.
Participants had to hold still and fixate while the system stimulated a small retinal region. Berkeley described the perceived patch as approximately fingernail-sized at arm’s length. This was not a full-scene replacement of everyday vision.
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What did the study establish—and what does “new color” mean?
In formal color matching, participants added white light to desaturate olo before matching it to the closest monochromatic light, which lies at the edge of the natural gamut. The authors interpret that result as evidence that the produced percept lay beyond the natural human gamut. Their paper, “Novel color via stimulation of individual photoreceptors at population scale,” was published in Science Advances on April 18, 2025: read the study.
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That is an operational finding about a percept under an experimental stimulation condition—not proof that olo exists as a color in the same sense as a wavelength or a pigment. The phrase “new color” is therefore open to interpretation. Vision scientist John Barbur, quoted by The Guardian, objected: “It is not a new colour.” His view does not negate the reported color-matching result; it highlights the difference between an unusual perceptual signal and a new color that ordinary light can produce. The Guardian’s coverage describes that debate.
Can you see olo on a screen, in paint or in a video?
No ordinary image, paint or consumer laser can recreate the experiment’s selective stimulation of mapped M cones. A screen can show a conventional teal-like approximation, but it cannot deliver the retinal input that produced olo. The Berkeley study’s images and videos document the experimental system; they are not a viewable sample of the percept for people watching on a display. An acrylic paint marketed as “olo” likewise cannot deliver the lab experience.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Why might Oz matter beyond this color claim?
The platform gives researchers a way to probe how specific photoreceptor signals shape vision. Berkeley researchers have pointed to possible studies of how vision changes when cones are lost or damaged. That is a research direction, not an established diagnostic service, treatment or demonstrated patient benefit. Berkeley’s overview explains the potential vision-science applications: How seeing the new color “olo” opens the realm of vision science.
For the original announcement and the researchers’ explanation of the percept, see Berkeley News’ report on olo and the UC Berkeley School of Optometry summary.
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