Olo: A New Color That Evolution Never Let You See

Summary

In April 2025, researchers at UC Berkeley unveiled 'olo,' a color that does not exist in nature and cannot be produced by any natural light source. Using the Oz system, a laser-based retinal display that images and targets individual cone cells in the living eye, scientists selectively stimulated only M (medium-wavelength) cones while leaving L and S cones inactive. Five subjects reported seeing an intensely saturated blue-green unlike anything producible by conventional light, since every natural stimulus inevitably 'spills over' onto neighboring cone types due to the ~85% overlap between M and L cone sensitivity curves. The article explains human trichromatic vision, the control experiment proving the effect, connections to philosophy's 'Mary's Room' thought experiment and tetrachromacy, and the implications for AI: any system trained on finite data has experiential 'dark rooms' it cannot reach without direct interaction with the physical world.