What happens when lasers hit just the right spot in your eye? Scientists have created a colour never seen before. Is this the start of new human senses?
Close your eyes and imagine a green so vivid it glows like neon. Now picture a blue so intense it feels alien. This is olo, a shade never before seen by human eyes—until now. In April 2025, five participants in a groundbreaking study glimpsed this “off-the-charts saturated” blue-green hue, created not by light but by lasers. The discovery, published in Science Advances, challenges how we define colour itself.
“It’s like spending your life in a pastel world and suddenly seeing neon,” says Professor Ren Ng, a computer scientist at the University of California, Berkeley, and one of the study’s authors. “Olo is so saturated, it doesn’t exist in nature.”
How the eye was hacked
Human colour vision relies on three cone cells in the retina: S (blue-sensitive), M (green), and L (red). Normally, these overlap—activating one cone always triggers its neighbours. But researchers used a laser system called Oz to isolate and stimulate only the M cones. By mapping each participant’s retina and tracking eye movements, they delivered precise light doses to individual cells.
The result? A signal the brain interprets as olo—a colour outside the natural spectrum. Unlike teal or peacock blue, olo’s “saturation” (intensity) exceeds anything sunlight can produce. Participants matched it to natural hues by diluting it with white light, akin to watering down paint.
The technology behind precision
The Oz system, detailed in the Science Advances paper, combines adaptive optics and real-time eye tracking to overcome biological barriers. A supercontinuum laser splits into infrared and visible wavelengths: the former maps the retina at cellular resolution, while the latter delivers microdoses of 543-nm or 488-nm light to individual cones. A Shack-Hartmann wavefront sensor and deformable mirror correct optical aberrations in the eye, ensuring laser focus remains diffraction-limited.
“Imagine painting with a brush thinner than a human hair, while the canvas wobbles,” explains co-author Austin Roorda, a vision scientist. “The eye never stops moving, so we track it at 960 frames per second. Each laser pulse adjusts its target in under 4 milliseconds.” This precision allows the system to bypass overlapping cone sensitivities—a feat previously deemed impossible outside theory.
A prophet’s vision realised
Two decades before olo’s discovery, evolutionary biologist Richard Dawkins speculated about “super green” hues in his 2004 book The Ancestor’s Tale. He imagined electrically stimulating a single cone to create colours “no real light could achieve.”
“This is precisely what’s been done,” Dawkins remarked after the study. “It’s rare for speculative ideas to materialise so elegantly.” The alignment of theory and experiment underscores how basic research can yield unpredictable breakthroughs.
Colour blindness and the brain’s limits
The study’s implications stretch beyond novelty. By artificially creating a third cone signal, the team hopes to help people with colour blindness—a condition affecting 1 in 12 men—distinguish hues they couldn’t before. Current gene therapies, tested in spider monkeys, add missing cones. Ng’s approach instead “hijacks” existing cells with lasers.
But challenges remain. The Oz system requires rare lab equipment and only works in a small visual field (twice the Moon’s apparent size). Still, Jenny Bosten, a neuroscientist at the University of Sussex, calls it “a technical triumph” for studying how the brain processes colour.
Is olo really a new colour?
Not all experts agree olo qualifies as “new.” Professor John Barbur, a vision scientist at City, University of London, argues it’s a matter of interpretation. “Stimulating cones differently alters perceived brightness or saturation, not hue,” he says. Historically, similar debates surrounded magenta—a “non-spectral” colour the brain constructs from opposing signals.
The team counters that olo’s uniqueness lies in its unprecedented saturation. “Natural colours are compromises,” says Ng. “Olo is pure M-cone activation—a solo instrument in an orchestra that usually plays in unison.”
The discovery arrives amid a surge in sensory-augmentation tech, from gene-editing trials for blindness to VR headsets that simulate synesthesia. Elon Musk’s Neuralink, which aims to merge brains with computers, recently teased a “coloured vision” mode for its implants. While olo’s lasers are invasive, they highlight a growing trend: hacking biology to expand human perception.
Spatial metamerism: A paradigm shift
Traditional colour displays, like RGB screens, rely on spectral metamerism—mixing wavelengths to mimic natural cone responses. Oz introduces spatial metamerism, controlling where light lands rather than its spectrum. This allows colours like olo, which exist outside the “bounded gamut” of natural vision.
“Think of it as playing a piano with keys that usually stick together,” says lead author James Fong. “Oz lets us press individual keys—M cones—without touching their neighbours. The brain hears a note it’s never encountered.” This approach could redefine industries from digital displays to medical imaging.
Challenges in colour control
Despite its promise, spatial metamerism faces hurdles. The Oz prototype stimulates just 0.9° of the visual field—roughly a thumbnail at arm’s length. Expanding this requires classifying millions of cones in real time, a task the team compares to “mapping a city during an earthquake.” Eye movements, even microsaccades, blur stimuli unless compensated at millisecond speeds.
The study also reveals perceptual quirks. Prolonged stimulation causes colours to fade, akin to Troxler’s effect. “Stability is the enemy,” notes co-author Hannah Doyle. “Colours only persist if we constantly ‘refresh’ cones with dynamic patterns.” This dynamism, visible in supplementary videos, shows red lines shimmering as lasers chase drifting cones.
What does this mean for science?
Beyond applications, olo probes fundamental questions. How does the brain turn retinal signals into conscious experience? Could we engineer entirely new senses? Kimberly Jameson, a colour-vision specialist at UC Irvine, says the technique lets scientists “explore the brain’s plasticity in ways previously unimaginable.”
For now, olo remains a lab curiosity. But as augmented reality and bioengineering advance, such experiments may pave the way for a world where humans see UV patterns like bees or navigate via magnetic fields—like birds.
Ethics and the future of vision
The ability to manipulate perception raises ethical questions. Could such technology be weaponised? Or deepen societal divides if only accessible to a few? The team acknowledges these concerns but emphasises foundational research. “We’re decoding the rules of vision,” says Ng. “How society uses them is a conversation for us all.”
Could you one day see olo on a smartphone screen? Probably not soon. Yet this research reminds us that reality is shaped by our biology—and that science can redraw its boundaries. As Dawkins mused, “What wonders remain invisible, simply because we lack the senses to perceive them?”
