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“Olo” is a reported blue-green visual percept produced when a 2025 experiment selectively stimulated retinal cells that ordinary light does not activate on their own. Five people saw it in the original study—not necessarily the only people to have seen it since. It is not a newly discovered wavelength, and a painting, color swatch, monitor or television cannot reproduce the experiment.
What is olo?
Olo is the name researchers gave to a highly saturated blue-green percept produced with their experimental Oz system. The study’s ideal target was to activate only medium-wavelength-sensitive (M) cone cells in the retina. Its authors described the resulting percept as beyond the range of colors people can ordinarily see, or the natural human color gamut.
That claim is about a visual experience created by a particular pattern of retinal stimulation. It does not mean scientists found a new wavelength of light. The researchers’ paper calls the work a proof of principle and a partial expansion toward a theoretical maximum, rather than a way to produce olo in ordinary viewing. Fong et al., Science Advances, 18 April 2025
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How did the Oz experiment produce it?
Human color vision commonly depends on three types of cone cells: short-wavelength (S), medium-wavelength (M) and long-wavelength (L). Ordinary light does not selectively activate M cones while leaving the others untouched. UC Berkeley’s 2025 account explains that 85% of light that activates M cones also activates L cones, which makes isolating the M-cone signal with natural light difficult.
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Oz was designed to target cones individually. The system mapped the retina using high-resolution imaging, tracked eye movements and delivered laser microdoses to selected cones. The paper reports a rate of 105 microdoses per second, across a visual field about 0.9° square positioned roughly 4° from the gaze-fixation target. Those are specifications of an experimental system, not a consumer display. UC Berkeley CDSS, 18 April 2025
In color-matching trials, participants added white light to desaturate the Oz percept until it matched the closest monochromatic light at the edge of the natural gamut. The study also tested what happened when the laser targets were jittered so that pulses landed on random neighboring cells. With precise targeting disrupted, participants’ matches moved toward the laser’s ordinary color, and they could no longer perceive the same image features. That control supports the researchers’ conclusion that accurate cone targeting mattered to the result. Science Advances study
Have only five people seen olo?
Five people saw olo in the original study, according to the paper and contemporaneous coverage. That number describes the study’s participants, not a confirmed worldwide total today. UC Berkeley Research reported in August 2025 that more people had seen olo since the initial work, but did not give a new total. Nature, 18 April 2025, corrected 22 April 2025; UC Berkeley Research, 19 August 2025
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Is olo really a “brand-new color”?
It depends on what “new” means. The researchers use the term because the M-cone-only signal does not arise in natural viewing and their color-matching results placed the percept beyond the natural gamut. In that scientific sense, olo is a percept made accessible by an unusual retinal input—not a new part of the light spectrum or a color everyone can encounter in daily life.
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The interpretation is disputed. John Barbur, a vision scientist at City St George’s, University of London, told The Guardian, “It is not a new colour,” describing the result instead as a more saturated green produced by stimulating M cones in someone with a normal red-green chromatic mechanism. That is an expert interpretation of what the result means; it does not erase the study’s measured matching results. The Guardian, 18 April 2025, updated 19 April 2025
Can you see olo in a picture or paint it?
No. A screen or printed image produces light or pigment mixtures within the ordinary ways those media stimulate vision; it cannot selectively activate mapped M cones in your retina. Austin Roorda, a vision scientist on the research team, told The Guardian, “There is no way to convey that colour in an article or on a monitor.”
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A paint sold as an approximation may suggest a vivid teal, but it is not the Oz percept. UC Berkeley Research explicitly notes that paint cannot make someone experience olo. A swatch, RGB or hex value, and color-picker sample would likewise be representations in ordinary viewing, not a reproduction of the experiment.
What could the research be useful for?
Oz is an experimental platform for investigating how patterns of retinal input shape visual perception. The researchers discuss possible uses in vision science, including studying the effects of cone loss by simulating it in people with healthy vision. Berkeley coverage also describes research directions involving color blindness and tetrachromacy. These are possibilities for research, not established treatments, clinical capabilities or consumer features. UC Berkeley CDSS; UC Berkeley Research
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