Bizarre optical illusion has people convinced this Coca Cola can is red — there is no red.

Some optical illusions continue to intrigue people long after they've gone viral online. One of the most mind-boggling images on the internet was the Coca-Cola Can illusion. Coca-Cola cans are often associated with the color red, and the illusion plays on this perception. Despite what it looks like, the can in the image is not red at all. The only colors present in the image are black, white, and teal. This illusion, shared by Akiyoshi Kitaoka, an experimental psychologist who specializes in visual phenomena, shows a Coke can against the backdrop of horizontal stripes, tricking the viewer's eyes into seeing shades of red where there are none.

At first glance, the can seems to be red, as one would expect a traditional Coke can to be. However, that's not the case if one zooms in and focuses on any specific part of the image. A Reddit user also shared a pixelated image of a person holding a Coca-Cola can which exhibited muted hues, but still seemed to be red. In another version of the photo, the can appeared to be blue, but when the viewer zoomed in, they couls only see black, white, and yellow colors. This type of illusion reportedly happens because of the way eyes and brains interpret contrast and color.

Several social media users shared their opinions in the comment section. One X user, @Mrsanjaytrivedi, wrote, "I think you are using different pattern intensities that emit RGB wavelengths. The cones in our eyes detect a range of overlapping wavelengths with a sensitivity that centers on what our brains interpret as red. And the same for green detecting and blue detecting cones." Another person with the username @ReneMalingre wrote, "This is mostly due to the color opponency of cyan/green-red where non-cyan is interpreted as red. Some expectation probably plays into it. Would work with blue-yellow I imagine. Opposite-colour afterimages work in a related way."

Similarly, one Reddit user, u/Vlodimir_Putin, explained, "It is white. This is an example of simultaneous color contrast, a phenomenon that occurs when two adjacent colors influence one another, changing your perception of the colors. The cones in your eyes make it seem like it is pink. Cones give your eyes good color vision but can also play tricks with your brain, hence why from a distance, ie not zoomed in, the color appears pink and why you see the can of Coke as “red” even though there is no red in the image. Essentially, the way your eyes see color in the first place is by contrasting it with other colors." Several others came up with similar comments.

The way the human brain processes and perceives colors is complex. Photographer and filmmaker Jared Bendis offered a different explanation through a demonstration of the Retinex effect, also known as color constancy. Essentially, the eyes are constantly adjusting to different types and levels of light, and the brain becomes skilled at filling in the gaps. Since this process is intricate, Bendis used a photo of a bowl of fruit to illustrate it. The trick, it seems, lies in how cone and rod receptors in the eyes respond to color and light, often leading to confusion in the viewer's brain.