You Can Trick Your Eyes Into Seeing a ‘Forbidden’ World—And Even Unlock What’s Invisible, Studies Show

5 min readHere’s what you’ll learn when you read this story:Your eyes have special cells called cones and rods that help you see the world around you. In a recent study, an international team of scientists solved a decades-long mystery and determined how cones work at the molecular level, which could help treat vision disorders in the future. There are also other visual puzzles that scientists are beginning to unravel, such as revealing colors that should otherwise be impossible. As an elementary schooler, your favorite color is a major part of your identity. It’s the shade your friends will draw your birthday cards in, the connecting theme between all your clothes, and probably the hue of your cool pencil case. But, as a child, I distinctly remember having the thought: What if my green is your blue? In other words, what if we all see the same colors differently—and how do we see them in the first place?Thanks to a new study published in the journal Science, researchers now understand at the molecular level how we see the rainbow-filled world around us. Still, even with the recent insights, there is more than meets the eye when it comes to visual perception—literally. But never fear: Scientists are beginning to shed light on those mysteries, too.When we look at an object, we are really perceiving how it reflects wavelengths of light. This is thanks to our photoreceptors, or specialized light-detecting cells called rods and cones. The human vision spectrum falls between ultraviolet and red light, allowing us to perceive more than 10 million colors. While this seems incredible, our eyes are wildly outshined by some animals. For instance, geckos have eyes that are 350 times more sensitive at night than humans, because our rod cells—which help us see in dark environments—don’t pick up any color. The secrets behind rods have long been understood, while cones have remained somewhat of a mystery.Understanding How We See ColorIn the recent study, a global team of researchers from China, Germany, and Australia looked at the cones—or the cells that allow us to see color—on an atomic level. Cones don’t “see” color itself; instead, they react to light wavelengths and send electrical signals to the brain. Then, those signals are processed and help us make sense of the world around us.Cones are made up of proteins called opsins, and there are three different versions of the molecule that make up our red, green, and blue photoreceptors. Each opsin contains the same vitamin A-derived molecule, called retinaldehyde, which is sensitive to light. The research team looked at flash-frozen samples of these opsins and studied how each type binds to the molecule differently.The team found that the “red and green opsins appear to use very different placement of chemical electronic charges around the retinaldehyde,” Trevor Lamb, PhD—a researcher at Australian National University—explains in a press statement. “We suspect this difference explains how they shut off faster than the blue opsin, and much faster than the rod pigment.”In other words, our eyes function like high-speed cameras, and the researchers believe that these different placements around the retinaldehyde are what control the shutter speed. The team’s findings could eventually help scientists develop more effective treatments for cone dystrophies, altered color vision, or other vision disorders. However, the researchers said they can’t elaborate on what the recent work may reveal about perception specifically, as it isn’t their direct area of expertise.Regardless, it’s safe to say that there are still some mysteries as far as our vision goes. For instance, there are entire color fields in front of our eyes—perhaps even while reading this article—yet we’re entirely blind to them. And this isn’t the only example of our eyes deceiving us. But scientists are beginning to unravel those mysteries, too.Impossible Colors—and How to See ThemIt’s hard to imagine the world any differently than we already see it. Tomatoes are red. Sunflowers are yellow. An orange is, well, orange—or so we think. As it turns out, reality (at least when it comes to the rainbow) isn’t as it truly seems.For instance, purple isn’t real; it’s merely a side effect of your brain sorting out some chaos—sorry purple lovers. Red and blue wavelengths are at opposite ends of the light spectrum. When you see the wavelengths at the same time, they clash, and your eyes and brain don’t know what to do, so the mish-mash registers as “purple.” In other words, the color doesn’t have a wavelength of its own, but is rather an optical illusion.Olo is yet another color that tricks our brains; it’s an extremely saturated blue-green, often described as “peacock green,” that researchers recently discovered. In a 2025 study published in Science Advances, a team of researchers from the University of California, Berkeley, attempted to stimulate just the M cones, which perceive medium greenish wavelengths. Thanks to an evolutionary hiccup, the wavelengths that naturally stimulate the M cones overlap with those that stimulate the L cones (which perceive long, reddish wavelengths). In other words, M cones are never activated on their own—until this study, that is.The team used a special laser technique that they dubbed “Oz,” after Frank Baum’s novel, The Wonderful Wizard of Oz. Oz uses a green laser to stimulate the cones. When a combination of the three cone cells—S (which perceive short wavelengths), M, and L—are stimulated, a person will see images in technicolor, according to a university press release. But when the laser delivered electrical pulses to primarily the M cone, it enabled participants to see olo, or the “greenest green.”On the other side of the coin, researchers have also blended colors together to create seemingly impossible hues. For instance, have you ever seen blue-yellow? Not green, but both colors simultaneously. How about red-green? In 2010, Vincent Billock, PhD, and Brian Tsou—who were both scientists at the U.S. Air Force Research Laboratory at the time—wrote an article for Scientific American explaining how they proved this was actually possible.The pair combined two methods: image stabilization and equal luminance, which is when two or more colors seem to have the same brightness. Billock and Tsou kept the sample size small, so as to only test fellow vision researchers, rather than artists or other laypeople. The combination of methods was “remarkably effective,” according to the researchers. In fact, six out of the seven participants saw the forbidden colors.“Sometimes the result looked like a gradient that ran from, say, red on the left to green on the right, with every possible shade of greenish red and reddish green in between,” the researchers wrote in the article. “Other times we saw red and green fields in the same place but at different depths, as if seeing one hue through the other without any discoloration of either of them. Often we saw a nice, uniform reddish green or bluish yellow fill the whole field.”While you won’t be able to see olo or red-green on your own—at least not anytime soon—next time you walk through the aisles at the grocery store or drive past a field of wildflowers, know that the rainbow before your eyes might not be what it seems. Perhaps there’s even an impossible color escaping your vision at this very moment.Emma Frederickson graduated from Pace University where she studied communication and media. Prior to her time as an editor, she was a freelance science reporter. She enjoys covering everything from shipwrecks to pimple popping, but her favorite topics include climate change, conspiracy theories, and weird biology. When she’s not writing, Emma can be found hopping between coffee shops on the hunt for the world’s best oat milk cappuccino.