Researchers in the United States have ventured beyond the bounds of human perception, claiming to unlock a colour no eye has ever seen—until now. Published in Science Advances, the paper describes an audacious experiment involving lasers, the retina, and a shade so intense it has been given its name: olo.
Human sight is famously trichromatic. We rely on three types of cone cells in the retina—S, M, and L—that respond respectively to short (blue), medium (green), and long (red) wavelengths of light. All colours we experience are the result of these three channels and the brain’s remarkable ability to combine and interpret their signals. It’s a system as elegant as it is limiting. The cones overlap in their sensitivities, and until now, no light source has stimulated one cone type without also affecting the others.
This is where the team, led by Ren Ng at the University of California, Berkeley, pushed perception into the surreal. The scientists precisely targeted individual cone cells using a laser-based system dubbed “Oz”—a nod to that famously technicoloured realm beyond the Kansas plains. The aim is to stimulate only the M cones, bypassing the conventional overlap that makes such isolation impossible under natural conditions.
The result was, reportedly, a shock to the senses. Five participants—including three of the researchers themselves—described the experience as witnessing a profoundly saturated blue-green colour unlike anything they had previously encountered. “Jaw-dropping,” said Ng. “It looked like an unprecedented colour signal. Incredibly saturated.”
But the real surprise may not lie in the colour itself, but in what it reveals: the plasticity—and perhaps the limitations—of the human visual system. What we call colour is not a property of the world but of perception. Olo doesn’t exist in the outside world, nor can it be printed, photographed, or rendered on a screen. The researchers shared an image of a turquoise square as a faint analogue, though they admit it is a poor substitute.
“There is no way to convey that colour in an article or on a monitor,” said Austin Roorda, a vision scientist on the project. “The whole point is that this is not the colour we see, it’s just not. The colour we see is a version of it—but it pales by comparison with the experience of olo.”
The name may feel whimsical, but the implications are weighty. The team’s optical sleight of hand raises philosophical and physiological questions: If a colour can only be seen under laboratory conditions, does it truly exist? Or is it simply a fleeting anomaly—visual poetry etched briefly into the brain, never to be seen again?
Either way, it’s an audacious leap into sensory terra incognita. For now, olo remains the domain of lasers and research labs—but like all great discoveries, its meaning may only be fully understood in time.
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