In what may be one of the most startling developments in the science of human perception, a team of researchers from the University of California, Berkeley, claims to have discovered a new colour—one that cannot be seen under natural conditions and cannot be reproduced by any screen, ink, or paint.
Dubbed “olo”, this colour reportedly emerged from an experiment that involved firing laser pulses into volunteers’ eyes to stimulate individual photoreceptor cells in a way that natural light cannot. The result: an allegedly unprecedented visual experience that has stirred both excitement and skepticism within the scientific community.
Beyond the Limits of Human Perception
Colours, as we commonly experience them, are created when different wavelengths of light stimulate three types of cone cells in the retina—L (long), M (medium), and S (short), roughly corresponding to red, green, and blue. However, no light in the natural world stimulates only one of these cone types in complete isolation. As a result, some theoretical colour combinations remain out of reach.
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That’s where the Berkeley research team came in. Led by electrical engineer Ren Ng and vision scientist Austin Roorda, the team sought to break through these natural limitations using pinpoint laser technology.
“We predicted from the beginning that it would look like an unprecedented colour signal,” Ng said, “but we didn’t know what the brain would do with it. It was jaw-dropping.”
The Birth of “Olo”
The researchers coined the name “olo” for the new hue, based on a binary system—“010”—that indicates stimulation of only the M (medium wavelength) cone cells, while L and S cones are left inactive. Normally, any perceived colour activates at least two of the three cone types.
To achieve this unique condition, the team began by precisely mapping the retina of each test subject to identify the exact location of individual M cones. Using a sophisticated eye-tracking system and laser pulses, they then stimulated only the M cones in a designated region of the retina, avoiding L and S cones altogether.
The result, they claim, is a colour that no human has ever seen through normal means—a greenish-blue unlike anything on the visible spectrum, deeper and more saturated than any digital display can replicate.
“This is not the colour we see on a screen,” Roorda explained. “It’s just not. The colour we see is a version of it, but it absolutely pales by comparison with the experience of olo.”
Too Vivid to Describe
To the five participants who witnessed olo, the hue defied conventional labels. Though they described it as “blue-green,” they acknowledged that words and images couldn’t do it justice.
The team did share an image of a turquoise square as the closest approximation, but stressed that it barely resembled the actual visual sensation experienced through laser stimulation. “There is no way to convey that colour in an article or on a monitor,” Roorda said.
The visible patch of olo appeared as a region about twice the size of the full moon, lingering in the field of vision before fading.
Scientific Implications and Skepticism
While the research, published in Science Advances, is being hailed as a milestone in the study of visual perception, not everyone is convinced. Professor John Barbur, a vision expert at City St George’s, University of London, was unimpressed.
“It is not a new colour,” Barbur argued. “It’s a more saturated green that can only be produced in a subject with a normal red-green chromatic mechanism when the only input comes from M cones.”
Barbur believes the perceived novelty stems from an unusual method of stimulation rather than an entirely new colour perception. “The work,” he added, “has limited value.”
Why It Matters
Despite the debate, the discovery may have profound implications for neuroscience, vision science, and even technology. The Oz Vision tool used in the experiment—named after the Emerald City in The Wizard of Oz—may allow scientists to explore how the brain constructs the rich tapestry of visual perception from simple cone signals.
“We’re now able to isolate the signal from a single class of cone and see what perception it creates,” Ng said. “That opens the door to understanding how combinations of these signals create the world as we know it—and how they might be failing in conditions like colour blindness or retinal disease.”
Beyond fundamental science, the approach could aid in diagnosing and treating degenerative eye conditions such as retinitis pigmentosa or age-related macular degeneration, and potentially even enhance understanding of neuroplasticity and sensory processing in the brain.
No Screens or Headsets Just Yet
Tempting as it may be to imagine olo appearing in your next smartphone update or VR headset, don’t expect to see it anytime soon. The colour can only be experienced via highly controlled, laser-based experiments that require real-time retinal tracking—technology far beyond commercial reach.
“This is basic science,” Ng reiterated. “We’re not going to see olo on any smartphone displays or any TVs. And this is very, very far beyond VR headset technology.”
Micro-Targeting the Eye: A New Frontier
One of the key advances of the Berkeley project lies not just in discovering olo, but in developing the precision optical tools that made it possible. The laser system they’ve created can track micro-movements of the eye and deliver light to single photoreceptor cells, something no previous system had achieved with this level of reliability.
“This opens up a whole new methodology in the study of colour,” Roorda said. “Not just how we perceive it, but how the brain processes and constructs visual information.”
A Long Path Ahead
There’s much still to learn. Can the experience of olo be replicated across people with different visual systems? What would this reveal about the diversity of human colour perception? Are there still other “impossible colours” waiting to be discovered using similar techniques?
Ng and Roorda believe they are just scratching the surface.
“We’ve always assumed that our perception of colour was bounded by the natural world,” Ng said. “But it turns out that those boundaries are imposed by light itself, not the brain. If we change the input, we may find the brain is capable of much more.”
For now, only five people have ever seen olo. But with further research, this new frontier in vision science may eventually illuminate more than just the colours of the world—it may change how we understand seeing itself.
