Researchers assert they have identified a 'new color'

A group of scientists asserts that they have identified a new color, described as a concentrated shade of blue-green, which cannot be observed with the naked eye without external stimulation.

The claim stems from an experiment conducted by researchers in the U.S., where laser pulses were directed into the participants' eyes. By activating specific cells in the retina, participants reported experiencing a color named "olo." However, some experts argue that the existence of this novel color is still a subject of debate. The study, published in *Science Advances* on Friday, has been characterized as "remarkable" by co-author Professor Ren Ng from the University of California. He noted that this shade is closest to the newly identified olo, which is significantly more saturated than any color typically visible. Prof. Ng, one of five participants in the study, shared insights on BBC Radio 4's *Today* program, stating that olo is "more saturated than any color you can see in the real world.

" He provided an analogy: if one has only ever seen pastel pinks throughout life, then encounters a vibrant baby pink and learns it is a new color called red, that experience mirrors what the participants encountered. During the experiment, researchers directed a laser beam into one eye of each participant. The study included five people—four men and one woman—all of whom had normal color vision. Notably, three of the participants, including Prof. Ng, helped author the research paper. According to the findings, participants were required to look into a specialized device called Oz, which incorporates mirrors, lasers, and optical elements. This equipment was previously developed by some of the researchers from UC Berkeley and the University of Washington and was adapted for the current study.

The retina, a light-sensitive tissue layer at the back of the eye, is crucial for processing visual information by converting light into electrical signals transmitted to the brain via the optic nerve. The retina contains cone cells, responsible for color perception, which come in three types—S, L, and M—each sensitive to different wavelengths of blue, red, and green, respectively. The research indicated that normally, light stimulating an M cone would also activate neighboring L or S cones due to overlapping functions. However, in this study, the laser selectively stimulated only M cones, theoretically sending a color signal to the brain that doesn't occur in natural vision. Consequently, olo cannot be perceived by the naked eye under typical conditions without specific stimulation. To validate the color perceived during the experiment, each participant manually adjusted a color dial until it matched olo. Some experts, however, contend that this new color is open to interpretation.

Prof. John Barbur, a vision scientist at City St George's, University of London, who did not participate in the study, noted that while this research represents a "technological achievement" in selectively stimulating cone cells, the claim of discovering a new color remains debatable. He explained that stimulating red cone cells in significant numbers could lead people to perceive a deep red, with perceived brightness influenced by changes in red cone sensitivity—a phenomenon similar to what was observed in this study. Despite the debate, Prof. Ng acknowledged that while olo is "certainly very technically difficult" to observe, the team is exploring the implications of these findings for color-blind individuals, who struggle to differentiate between certain hues.
BBC