Olo (color)

Olo is an imaginary color that can only be seen using specialized tools that exclusively activate the M cone cells on the retina, without activating the L and S cone cells at the same time. It is impossible to view olo under normal viewing conditions, due to the overlapping sensitivities of M cone cells and S and L cone cells in all wavelengths of visible light. In other words, there is no monochromatic stimulus (the purest type of stimulus that humans can perceive) that activates only the M cones. This means that olo is outside the visible gamut. To get around this, researchers mapped a portion of the retina and individually identified each cone cell as either an S, M, or L cone. They then used lasers to deliver tiny doses of light, targeting the M cone cells and mostly avoiding the S and L cone cells. This was achieved by applying adaptive optics to scanning laser ophthalmoscopy. The researchers who experienced olo said that the closest color to olo in the sRGB gamut is hexadecimal code #00FFCC.