Berkeley Researchers Laser-Target Cone Cells to Show 5 People a Color Called 'Olo'

UC Berkeley scientists reported on April 18, 2025 that they induced perception of a color no human can normally see. Dubbed ‘olo’ — after its (0, 1, 0) LMS color-space coordinates, which read as the word in leetspeak — the hue sits outside the visible gamut because no natural wavelength stimulates the retina’s M cones without also triggering the neighboring S and L cones. The team mapped a patch of retina, classified each cone individually, and fired precisely aimed laser pulses to activate M cones in isolation. Five subjects saw the result and described it as a blue-green of extreme saturation; the nearest sRGB approximation is #00FFCC.

The method, not the color itself, is the real achievement: per-cone stimulation at population scale is a hard engineering and imaging problem. Co-author Ren Ng framed the work as more than a novelty, suggesting the same targeted-stimulation approach could help manage color blindness or even push perception toward tetrachromacy — a wider color range than typical human vision.

The claim has drawn pushback. Critics, including vision scientist John Barbur, argue that whether olo qualifies as a genuinely ‘new’ color is debatable rather than settled, since it is a lab-forced perceptual state rather than a color present in the world. That skepticism, alongside interest from artists and the press, has made the result as much a story about how we define perception as about the technique behind it.