The colour closest resembles a light teal: Imagine seeing a colour that does not exist in the natural world. A shade so pure, so saturated, that your brain has never had reason to create it. For millennia, this was impossible. The physics of light and the biology of the eye conspired to keep this experience forever out of reach.
Until now.
Scientists at the University of California, Berkeley, have achieved a breakthrough that sounds like science fiction. They have enabled human beings to perceive a new colour—a dazzling, impossibly saturated blue-green they have named “olo.” Only five people have seen it. The rest of humanity must rely on description, approximation, and wonder.
This is the story of how precision lasers, a dash of Wizard of Oz inspiration, and a radical new understanding of the eye rewrote the limits of human perception.
Table of Contents
The Astonishing Find: A Colour with No Wavelength
For centuries, we believed the rainbow held all the colours we could ever see. Red, orange, yellow, green, blue, indigo, violet—each corresponds to a specific wavelength of light. Mix them, and you get the millions of hues that paint our world.
But there is a catch.
Every colour we perceive is a blend of signals from three types of cone cells in our retina. S-cones detect short wavelengths (blue). M-cones detect medium wavelengths (green). L-cones detect long wavelengths (red). The brain mixes these signals. That is the entire palette of human vision.
The limitation is fundamental. As Professor Ren Ng explains:
“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.”
This overlap has always constrained us. Until the Berkeley team found a way to break the rules.
The Oz Technique: Lasers, Mirrors, and the Emerald City
The breakthrough required a radical approach. Instead of trying to find a light source that stimulated only M-cones—an impossibility in nature—the team decided to target individual cells with surgical precision.
They named their method “Oz” after the Emerald City in The Wizard of Oz. The reference is deliberate. As Ng puts it:
“There’s a journey to the Emerald City, where things look the most dazzling green you’ve ever seen.”
The experimental setup was anything but comfortable. Participants entered a darkened laboratory filled with lasers, mirrors, deformable mirrors, modulators, and light detectors. Each volunteer had to bite down on a bar to keep their head perfectly still. Lasers mapped their retinal cone cells at the individual level.
Then came the moment of magic.
A precision laser delivered light exclusively to M-cone cells, completely bypassing their S and L neighbors. For the first time in human history, the brain received a signal it had never experienced: pure M-cone activation, untainted by any other input.
The result was a thumbnail-sized square of unprecedented colour. The brain, confronted with this novel signal, synthesized a perception that has no equivalent in the natural world. They named it olo.
What Olo Looks Like: Approximating the Impossible
Describing a colour no one else can see is a challenge. The closest approximation on a standard computer screen is a vibrant teal, specifically the hexadecimal code #00ffcc. But Ng cautions that olo extends far beyond any displayable colour. It is “blue-green with unprecedented saturation.”
Imagine the most intense turquoise you have ever seen. Then multiply its vividness beyond anything your screen can produce. That is the direction of olo, if not the reality.
Verification experiments confirmed the phenomenon was real. When researchers added white light to desaturate olo, it matched a standard teal laser. The perception was consistent, repeatable, and measurable.
The Experience: What the Five Saw
Only five people have witnessed olo directly. Ng himself was among them, along with two other study co-authors and two additional participants. Their descriptions align: a colour of shocking purity, unlike anything in their visual memory.
The experience was brief. The laser spot was small. The setup was demanding. But for those moments, they stood at the frontier of human perception.
Manuel Spitschan from the Max Planck Institute for Biological Cybernetics called the work:
“A fascinating study, a truly groundbreaking advance in the ability to understand the photoreceptor mechanisms underlying colour vision.”
Global Implications: Rewriting the Biology of Sight
This discovery does more than add a novelty to the colour wheel. It fundamentally changes our understanding of how vision works.
For decades, the model of colour perception assumed that the brain’s experience was entirely determined by the mix of wavelengths entering the eye. The Berkeley experiment proves that the brain is capable of generating novel colour experiences when presented with signals it has never encountered.
This opens extraordinary possibilities.
Imagine tailored visual experiences that bypass the limits of physical light. Imagine correcting colour blindness by directly stimulating specific cone populations. Imagine virtual reality that renders hues no screen can produce. The Oz technique is a proof of concept for a new kind of visual engineering.
It also raises profound philosophical questions. If colour exists only in the brain, and we can now create colours without corresponding wavelengths, what does “real” colour even mean? Olo is as real as any colour you have ever seen. It simply originates in a laser and a neuron, rather than a sunbeam and a rose.
What This Means for History: The Expanding Sensory Universe
Human beings have always been limited by our biology. We see a sliver of the electromagnetic spectrum. We hear a narrow band of sound. We smell only a fraction of the chemical world. These limits define our reality.
But they are not absolute.
The discovery of olo demonstrates that our sensory limits can be transcended through technology. We are not trapped forever within the boundaries of evolution. We can build tools that extend perception, create new experiences, and reveal worlds hidden in plain sight.
The five people who saw olo are pioneers. They glimpsed a colour that no human had ever seen, that no natural object could produce. They stand at the threshold of a new frontier.
Future generations may look back on this moment the way we look back on the first flight, the first moon landing, the first glimpse of a distant galaxy. It is a reminder that the universe is larger than we know, and that our tools can take us further than our biology ever could.
Olo is just the beginning.
In-Depth FAQs: Your Questions Answered
1. How is “olo” different from any other colour?Every other colour we perceive results from a combination of signals from the three cone types in our eyes. Olo is unique because it results from activating only one type of cone (the M-cones, sensitive to green) in isolation. This has never happened naturally, because any real light source that stimulates M-cones will also stimulate S or L cones to some degree.
2. Can I see olo on my computer screen?No. Computer screens create colours by mixing red, green, and blue light. This process inherently stimulates multiple cone types simultaneously. The closest approximation is the hex code #00ffcc, a vibrant teal, but this is only a dim echo of the actual olo experience. True olo cannot be displayed on any existing screen.
3. Why is this discovery described as “impossible”?It was considered impossible because of the principle of univariance—the idea that a given cone cell’s response conveys only intensity, not colour. To perceive a unique hue, you need differential activation across cone types. The Berkeley team bypassed this by targeting individual cones with extreme precision, creating a neural signal the brain had never processed.
4. What practical applications could this have?Potential applications include advanced vision research, treatments for colour blindness (by directly stimulating dormant or deficient cones), and next-generation virtual and augmented reality that could produce colours beyond the limits of current display technology. It also opens new avenues for understanding how the brain constructs perceptual reality.
5. Will more people get to see olo?The research team hopes to refine the technology, making it more accessible. Currently, the setup is complex, expensive, and demanding for participants. As the technique develops, it may become possible for more people to experience olo and for scientists to explore other “impossible” colours by targeting different combinations of cone cells.
