Dr. Phlip McMillan,  John McMillan

Imagine seeing a color that no human has ever seen before. A team of scientists from the University of California, Berkeley, and the University of Washington has done just that. They have developed a new technique that allows people to perceive a color previously outside the natural range of human vision. The researchers have named this novel color “olo.”

A Step Beyond the Visible Spectrum

Human eyes use three types of cone cells to perceive color: long (L), medium (M), and short (S), which are most sensitive to red, green, and blue light, respectively. Normally, these cones are activated together in overlapping patterns, allowing us to see a wide variety of colors. But this overlap also places limits on what we can perceive. The researchers wondered what would happen if they could activate only one type of cone—specifically, the M cones—without stimulating the others. According to theory, this would send a completely new signal to the brain, one that does not occur in everyday visual experience. The result could be a new color entirely.

Introducing Oz

To test this theory, the scientists created a method called “Oz,” named in tribute to the land of Oz from the classic story. The method uses advanced imaging and laser technology to pinpoint the exact location of cone cells in a person’s retina. Once mapped, the system directs laser light to activate only the M cones. The technique requires precise timing and targeting. Laser microbursts are delivered over 100,000 times per second, adjusting in real time to the tiny movements of the eye. The outcome was extraordinary. Participants reported seeing a bright blue-green hue, one unlike any known color. This new color was named “olo,” inspired by the 0-1-0 coding pattern that represents activation of only the M cones.

A New Kind of Color Experience

After discovering olo, the team used it to create visual scenes. Participants viewed photos and short videos with the olo color incorporated into the background. They were able to clearly distinguish shapes and motion in these scenes, confirming that olo could be used as part of a broader visual experience. To test the accuracy of their method, researchers ran control trials. When the laser was slightly misdirected, the color appeared normal and the distinctive olo effect vanished. This confirmed that seeing olo depended entirely on precise stimulation of the M cones alone.

Implications for Science and Vision

The ability to create a new color using targeted retinal stimulation has exciting potential. The researchers believe that this technique could help in studying and perhaps treating color vision deficiencies. For instance, by mimicking the effect of a fourth cone type, they may be able to simulate what vision is like for people with tetrachromacy—a rare condition where individuals can see a broader range of colors. This method could also serve as a valuable tool in neuroscience. For the first time, scientists have precise control over the first layer of visual input to the brain. This could lead to new insights into how we perceive the world and how the brain adapts to artificial sensory information.

Looking Ahead

Currently, the technology works only within a small area of the retina and requires the subject to keep their gaze fixed. Expanding the field of view and adapting it for natural eye movements will be key challenges for future research. Still, the achievement is groundbreaking. Scientists have shown that by changing how we stimulate the eye, we can expand the range of what it is possible to see. Olo may be just the beginning. As one of the lead researchers put it, “We are not just showing new colors – we are discovering them.”   Reference:  James Fong et al, Novel color via stimulation of individual photoreceptors at population scale, Science Advances (2025)