Have scientists discovered a new colour called ‘olo'?

Al Jazeera

26-04-2025

A team of scientists claims to have discovered a new colour that humans cannot see without the help of technology.
The researchers based in the United States said they were able to 'experience' the colour, which they named 'olo', by firing laser pulses into their eyes using a device named after the Wizard of Oz.
Olo cannot be seen with the naked eye, but the five people who have seen it describe it as being similar to teal.
Professors from the University of California, Berkeley and the University of Washington School of Medicine published an article in the journal, Science Advances, on April 18 in which they put forth their discovery of a hue beyond the gamut of human vision.
They explained that they had devised a technique called Oz, which can 'trick' the human eye into seeing olo. The technique is named after the Wizard of Oz.
In the Wonderful Wizard of Oz, published in 1900, Frank Baum wrote about a man who uses tricks to fool the residents of the fictional land of Oz into thinking he's a wizard. For instance, it is believed that the Emerald City, the capital of Oz, is so bright and vibrant that visitors have to wear special glasses to protect their eyes. The glasses are one of the wizard's tricks, since they make the city appear greener and grander.
The human eye perceives colour via three types of photoreceptor or 'cone cells' in the retina. S cones pick up shorter, blue wavelengths of light; M cones detect medium, green wavelengths; and L cones detect longer, red wavelengths.
'The signals from these cones are then sent through a complex series of cells in the retina that act to clean up and integrate the signal before passing it down the optic nerve through parts of the brain,' Francis Windram, a research associate at the department of life sciences at Imperial College London, told Al Jazeera.
The part of the brain that the visual information is passed to is the visual cortex.
In normal vision, the function of M cones overlaps with the neighbouring S and L cones, so any light that stimulates M cones also activates the other two cones. The M cones don't function alone.
'There's no wavelength in the world that can stimulate only the M cone,' Ren Ng, a professor of electrical engineering and computer sciences at UC Berkeley, explained in an article published on its website.
'I began wondering what it would look like if you could just stimulate all the M cone cells. Would it be like the greenest green you've ever seen?'
So Ng teamed up with Austin Roorda, one of the creators of the Oz technology and a professor of optometry and vision science at UC Berkeley.
Oz, which Roorda described as 'a microscope for looking at the retina', uses tiny microdoses of laser light to target individual photoreceptors in the eye. The equipment, which must be highly stabilised during use, is already being used to study eye disease.
The work using Oz began in 2018 by James Carl Fong, a doctoral student in electrical engineering and computer sciences at UC Berkeley. Hannah Doyle, another doctoral student at Berkeley, ran the experiments through which human subjects were able to see the new colour, olo.
The shade of olo has always existed, it just falls beyond the spectrum of shades visible to the human eye. There are other such shades that we cannot see. Hence, olo is not a new colour that has come into existence, from a physical or scientific perspective.
However, 'from a sociolinguistic perspective, if people give new names to colours which previously were indistinguishable thanks to this technology, then maybe! It all depends on how you say it,' Windram said.
Five people have seen the 'new' colour – four men and one woman. All had normal colour vision.
Three of the subjects, including Roorda and Ng, are the co-authors of the research paper while the other two are members of the participating lab at the University of Washington and were unaware of the purpose of the study before they took part.
Those who have seen olo describe it as a teal or green-blue colour – but one they had never seen before.
In the article by UC Berkeley, it is described as a 'blue-green colour of unparalleled saturation'.
'It was like a profoundly saturated teal … the most saturated natural colour was just pale by comparison,' Roorda said.
'I wasn't a subject for this paper, but I've seen olo since, and it's very striking. You know you're looking at something very blue-green,' Doyle said.
The researchers said an image of a teal square is the closest colour match to olo. However, this square is not an olo-coloured square. The naked human eye simply cannot see the shade.
'We're not going to see olo on any smartphone displays or any TVs any time soon. And this is very, very far beyond VR headset technology,' Ng said, according to a report in the UK's Guardian newspaper.Berkeley researchers are exploring whether the Oz technology could help people with colour blindness.
Windram said success would depend on the cause of colourblindness in individuals. Deuteranomaly, which causes decreased sensitivity to green light, is the most common form of colour blindness.
'In this case, a miniaturised version of this technology could theoretically be used to correct this by directly stimulating the cones when the correct colour of light hits them,' Windram said.
Windram pointed out that publicity materials for the research show images of the Oz experiment on a highly stabilised table.
'This would require a lot of work to miniaturise the technology, and is likely a long way off. Given that the laser must stably hit the correct cones in order to stimulate them, this may not really be feasible as a form of vision correction technologically,' he said.
The concept of a colour has three main components, Windram explained: The physical, which has to do with the wavelengths of light that meet the eye; the neurological, which refers to how humans biologically process these light signals; and the societal or linguistic component, which pertains to how colours are named.
'In the end I may see a colour and call it 'red', someone else may call it 'rot' or 'rouge' … but also another may look at it a bit more closely and say 'well it's claret' or 'crimson'.'
To test this, neuroscience and AI researcher Patrick Mineault developed a website for entertainment purposes in September 2024, on which users can take a test to see how their colour perception compares to others.
Humans can also perceive colour differently due to differences in factors such as 'temperature' of light. This was demonstrated when a photo of a dress went viral in 2015, dividing social media users over whether the dress was white and gold, or blue and black.
Windram explained that people who were deciding what colours the dress was were drawing on preconceived notions of whether the photograph of the dress was taken in warm lighting or cool lighting.
Yes, different species can experience colours differently.
For example, humans process three wavelengths corresponding to red, blue and green light, while the mantis shrimp, a tiny crustacean, can visually perceive 12 channels of colour instead of three. An article by the Australian Academy of Science explains that the mantis shrimp can also detect ultraviolet and polarised light, which humans cannot see.
However, while the human eye can mix two colours and perceive an in-between shade – such as purple as a mix of red and blue – the mantis shrimp's eyes cannot mix colour receptors.
Meanwhile, dogs only have two types of cones and can mostly only see shades of yellow and blue.