A group of scientists in the United States say they have discovered a new colour, never before seen by the human eye, through an innovative experiment that involved directing laser pulses into participants' eyes.
The colour, which researchers have named "olo", was reportedly witnessed as a vivid blue-green hue during a study aimed at stimulating specific cells in the retina, BBC reports.
While the finding, published in Science Advances on Friday, has drawn interest and curiosity, some experts remain sceptical, calling the claim “open to argument”.
Professor Ren Ng of the University of California, one of the study’s co-authors and also a participant, described the results as “remarkable”. He explained that olo appeared to be “more saturated than any colour that you can see in the real world”.
He likened the experience to spending a lifetime seeing only muted tones of pink, only to one day encounter an extremely intense shade that is then revealed to be an entirely different colour—red.
“Let’s say you go around your whole life and you see only pink, baby pink, a pastel pink,” he said. “And then one day you go to the office and someone’s wearing a shirt, and it’s the most intense baby pink you’ve ever seen, and they say it’s a new colour and we call it red.”
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The experiment involved five individuals—four men and one woman—all of whom had normal colour vision. Three of the participants, including Prof Ng, were also co-authors of the study.
In the procedure, a laser beam was directed into the pupil of one eye of each participant using a device known as “Oz”, which is equipped with mirrors, lasers and other optical instruments.
The device was developed by researchers from UC Berkeley and the University of Washington, and modified specifically for this research.
At the heart of the experiment is the retina, the light-sensitive tissue at the back of the eye responsible for processing visual information. It contains cone cells, which are responsible for colour perception. There are three types of cone cells in the human eye—S, M and L—each responsive to different wavelengths of light: short (blue), medium (green), and long (red), respectively.
In typical vision, stimulating the M cone cells (sensitive to green) also results in some level of activation in either the L (red) or S (blue) cones, due to overlapping functions. But in this experiment, researchers managed to isolate and stimulate only the M cones. This selective activation created a visual signal that does not naturally occur, resulting in the perception of a new colour—olo.
“This in principle would send a colour signal to the brain that never occurs in natural vision,” the study explained. Participants then used a controllable colour dial to match the colour they had perceived, thereby attempting to validate the existence of olo.
Despite the enthusiasm of the research team, not all experts are convinced. Professor John Barbur, a vision scientist at City St George’s, University of London, who was not involved in the study, commended the team for their technological achievement in stimulating cone cells, but expressed doubts about whether this constitutes the discovery of a genuinely new colour.