NEW YORK, April 23: For the first time, humans may have caught a glimpse of colors that were previously invisible to the human eye — including what researchers describe as a “blue-green of unprecedented saturation.”

These colors exist in a spectrum beyond our natural visual range. Under normal circumstances, human eyes simply can’t detect them. But researchers from the University of California, Berkeley, and the University of Washington say they've developed a way to artificially expand the human color palette by manipulating how the retina processes light.

Using a prototype device dubbed “Oz,” the scientists believe they can alter the way cone cells in the eye send color signals to the brain — essentially creating visual experiences outside of our natural perception. These new signals can't be produced by natural light alone.

The Oz prototype uses a laser to flash monochromatic light, usually green, directly at individual cone cells in the retina — the specialized cells responsible for detecting color. Human eyes contain over six million of these cone cells, which come in three types: L (long wavelength, red), M (medium wavelength, green), and S (short wavelength, blue). Together, these allow us to perceive the full range of visible color.

In natural conditions, colors stimulate a mix of cone cells. But the Oz device uniquely targets only the M cones, creating a signal that doesn't naturally occur. During testing, three participants stared at a neutral gray background while their M cones were stimulated with the laser. The color they perceived didn’t match any known hue — even when given red, green, and blue lights to compare it with. To make a match, participants had to add significant amounts of white light, suggesting the color was exceptionally saturated and novel.

The researchers named this unfamiliar color “olo.” Its closest visible approximation was shown in comparison boxes, though it still didn't fully capture the hue seen by participants.

In another experiment, moving patterns were presented while selectively targeting different cone cells. Participants reported seeing dynamic colors and imagery that don’t exist in the natural world — such as vivid red lines or rotating dots set against an “olo” background.

These findings suggest that with precise stimulation, it may be possible to experience an entirely new visual spectrum — potentially even in videos or digital displays.

However, not all experts agree on the implications. Vision scientist John Barbur of the University of London, who was not involved in the research, called the team's claim of a “new color” debatable. While he praised the technical achievement of targeting specific cones, he cautioned that the effect might simply intensify familiar colors rather than introduce truly new ones.

There are also limitations. The Oz prototype only worked on peripheral vision, as cone cells are less densely packed and more accessible at the edges of the retina — though these areas offer lower clarity.

Despite these challenges, the research team believes this is just the beginning. They hope to refine their device for deeper exploration of the human visual system — and possibly even to develop treatments for color blindness.

“Oz represents a new class of experimental platform,” the team wrote, “designed for complete control over the eye’s initial signal to the brain, enabling activation of individual photoreceptors at precise moments.”

They believe this prototype is a significant step toward that level of neural precision — and a bold leap into an unseen world of color.