Scientists have been able to trick the human eye with lasers, enabling them to see a new colour, never seen before. The “off-the-charts saturated” greenish hue called olo has been seen by only five study participants.
The researchers used the lasers and tracking technology to selectively activate certain cells in the study participants’ retinas.
It is not the first time researchers have stimulated individual cone cells, the photoreceptors in the eye whose signals the brain interprets as colour. But this time it was done across an area large enough to alter a person’s vision substantially.
The findings, published in the journal Science Advances,1 have been described by the study’s co-author, Prof Ren Ng from the University of California, as “remarkable”.
… the colour olo could not be seen by a person’s naked eye in the real world without the help of specific stimulation.
Prof Ng, the study’s co-author and one of five people to take part in the experiment, told BBC Radio 4’s Today programme that olo was “more saturated than any colour that you can see in the real world”.2
“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 its a new colour and we call it red.”
There are three types of cone cells in the eye – S, L, and M – and each one is sensitive to different wavelengths of blue, red, and green respectively.
According to the research paper, in normal vision, “any light that stimulates an M cone cell must also stimulate its neighbouring L and/or S cones”, because its function overlaps with them.
However, in the study, the laser only stimulated M cones, “which in principle would send a colour signal to the brain that never occurs in natural vision”, the paper said.
This means the colour olo could not be seen by a person’s naked eye in the real world without the help of specific stimulation.
To verify the colour observed during the experiment, each participant adjusted a controllable colour dial until it matched olo.
Prof Ng admitted that although olo is “certainly very technically difficult” to see, the team is studying the findings to see what it could potentially mean for colour blind people, who find it difficult to distinguish between certain colours.
References
- Fong J, Doyle HK, Ng R, et al. Novel color via stimulation of individual photoreceptors at population scale. Sci Adv. 2025 Apr 18;11(16):eadu1052. doi: 10.1126/sciadv.adu1052. Epub 2025 Apr 18.
- Khalil, H. Scientists claim to have discovered ‘new colour’ no one has seen before, BBC, available at: bbc.com/news/articles/clyq0n3em41o [accessed 22 Apr 2025].
