Scientists report discovery of new colour through laser eye stimulation

A team of researchers in the United States say they have discovered a colour never previously seen by the human eye. Named “olo”, the colour emerged during an experiment using precise laser stimulation to isolate specific cells in the retina.

The study, published in Science Advances, involved five participants with normal colour vision. Researchers targeted the M-cones, the retinal cells responsible for detecting green light, without simultaneously activating neighbouring cones.

Under natural conditions, stimulating one type of cone invariably affects others, making this isolated stimulation impossible without artificial means.

Participants described the colour as a vivid blue-green unlike any real-world hue. One of the researchers, Professor Ren Ng of the University of California, also took part in the trial. He said the sensation was unlike anything in daily experience. “It was more saturated than any colour you can see in the real world,” he told BBC Radio.

Ng compared the sensation to seeing red for the first time after a life spent only viewing pastel pink. “It’s like stepping into a world with a new dimension,” he said.

The experiment used a device named “Oz”, which combines mirrors and lasers to direct precise light pulses into the eye. The system was developed by scientists from UC Berkeley and the University of Washington, and updated specifically for this study. Participants adjusted a colour dial to match the visual experience, helping researchers standardise the result.

Normally, human vision relies on three types of cone cells: S (blue-sensitive), M (green-sensitive), and L (red-sensitive). Light entering the eye stimulates overlapping cone types, which blend signals to produce the full visible spectrum. In this case, the isolation of M-cones triggered a neural response not found in everyday vision, resulting in the perception of a previously unseeable colour.

The researchers say the experiment demonstrates that the brain is capable of processing unique sensory data when exposed to targeted input, potentially expanding the known boundaries of human perception.

Not all experts agree with the interpretation. Professor John Barbur, a vision scientist at City St George’s, University of London, called the work a technical achievement but questioned whether it truly represents the discovery of a new colour. He said similar effects can result from varying the sensitivity of cone cells, which would affect brightness and contrast without producing a categorically new hue.

Barbur added that perceptions triggered through artificial stimulation may not qualify as distinct colours in the conventional sense. “This is open to argument,” he said.

Ng acknowledged the complexity of the claim but defended the findings. He and his colleagues believe the experiment has implications for vision science, particularly for understanding how the brain processes colour information. They are also exploring whether the method could support new approaches to colour blindness.

The colour olo cannot be observed naturally and does not exist on the traditional colour wheel. Its existence is dependent on specific laboratory conditions involving direct retinal stimulation.

Though participants perceived the same general experience during testing, the colour remains difficult to categorise. Ng and his team describe it as a highly saturated shade of blue-green, but stress that it occupies a perceptual space inaccessible through ordinary light exposure.

Further research is under way to determine whether the technique can reveal additional novel visual effects or be applied to enhance visual aids. The team also plans to investigate whether variations of the method could benefit individuals with impaired colour discrimination.

HT

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