Using laser pulses aimed at individual cone cells, UC Berkeley researchers produced a visual experience impossible with any natural light — and named it "olo."
Imagine being handed a crayon labelled a colour you have never seen before — not a shade of existing colours, but something entirely new. That is approximately what a small group of volunteers experienced inside a lab at the University of California, Berkeley in early 2026. Researchers stimulated individual cone cells in the human retina using precisely aimed laser pulses, producing a visual sensation they have named "olo" — a saturated blue-green the likes of which no wavelength of light in nature can produce.
Your retina contains three types of cone cells — S (short wavelength, blue), M (medium wavelength, green), and L (long wavelength, red). Every colour you have ever seen is a combination of signals from these three cell types working together. The problem is, you cannot stimulate just one type of cone with ordinary light. When you look at a green object, both M and L cones respond, and your brain mixes those signals into what you perceive as green.
Participants in the study described the colour as extraordinarily vivid — a saturated teal-green that seemed to glow with an internal quality no surface colour could match. Some likened it to imagining a colour, except it was unmistakably real and external. One participant, a graphic designer, said it was "like hearing a note that no instrument can produce."
"The experience was unlike anything I can point to in the world. It was not just a different shade — it was a fundamentally different category of experience."
— Study participant, UC Berkeley, 2026The researchers are careful to note that "olo" is not a supernatural phenomenon. It is simply the brain's response to a pattern of cone stimulation that ordinary physics prevents from happening naturally. Light of any wavelength will always activate multiple cone types to varying degrees. Only by targeting individual cells with a laser can you produce pure, isolated M-cone activation — and the result is a colour your visual system has never had the input to generate before.
The implications reach well beyond the fascination of a new colour. The OISL technology that made this possible can stimulate individual photoreceptors with extraordinary precision — opening doors to treatments for colour blindness, macular degeneration, and other vision disorders. If researchers can selectively activate or bypass damaged cells, they may be able to restore sight in ways that conventional medicine cannot. The study's lead author described the new colour as almost a side effect of a tool built for therapeutic purposes.