Scientists claim they have discovered a new colour called ‘olo’.
The snag is that it’s only ever been witnessed by five people in the world – and cannot be seen by the naked eye.
Indeed, the colour, said to be a saturated shade of blue-green, cannot be seen without the help of stimulation by laser.
The researchers from UC Berkeley and the University of Washington had laser pulses fired into their eyes. This Oz Vision System technique, named in homage to the Emerald City in L. Frank Baum’s novel “The Wonderful Wizard of Oz” (and the subsequent 1939 film starring Judy Garland), can allow people to see beyond the normal gamut of colour perception.
The study, published in the journal Science Advances, states that when Oz laser signals are intentionally “jittered” by just a few microns (one millionth of a metre) subjects perceive the stimulating laser’s natural colour.
There are three types of cone cells in the eye – S (short), L (long) and M (medium) - each one sensitive to different wavelengths of light. By stimulating only M cones, the five participants claim to have witnessed a blue-green colour that scientists have called "olo" - denoting the binary 010.
The paper read: “We name this new color ‘olo’. Subjects report that olo in our prototype system appears blue-green of unprecedented saturation, when viewed relative to a neutral grey background. Subjects find that they must desaturate olo by adding white light before they can achieve a colour match with the closest monochromatic light, which lies on the boundary of the gamut, unequivocal proof that olo lies beyond the gamut.”
The study's co-author, Professor Ren Ng from the University of California, has described the findings as "jaw-dropping".
“We predicted from the beginning that it would look like an unprecedented colour signal but we didn’t know what the brain would do with it,” said Professor Ng. “It was jaw-dropping. It’s incredibly saturated.”
Prof Ng told BBC’s Radio 4’s Today programme that olo was "more saturated than any colour that you can see in the real world".
"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."
While it does not fully capture the colour, the researchers shared an image of a turquoise square to give a sense of the hue:
However, they stressed that the colour could only be experienced through laser manipulation of the retina.
The claim of a new colour has been contested, however.
“It is not a new colour,” said John Barbur, a vision scientist at City St George’s, University of London. “It’s a more saturated green that can only be produced in a subject with normal red-green chromatic mechanism when the only input comes from M cones.”
The work, while a “technological feat”, has “limited value” according to Barbur.
The authors of the study disagree. They believe ‘Oz’ will help them delve into how the brain creates visual perceptions of the world. As reported by the BBC, it may also allow them to learn more about colour blindness or diseases that affect vision.
Well, there's no place like home... Sorry, no colour like olo.
Dorothy would be proud.
