Photo by Jeanson Wong on Unsplash

We know Coca-Cola cans are red, but that's not why it looks red in a viral optical illusion.

Optical illusions are wild. We can look at an image and swear up and down we see one thing, only to find out what we're seeing isn't what we're actually seeing at all.

Some optical illusions regularly go viral, like the not-really-two-dogs photo or the cat going up or down stairs drawing or the moving Van Gogh painting. (And we all remember the debates over "the dress," right?)

One that's making the rounds now is an image that appears to be a pixelated photo of someone holding a Coca-Cola can. The colors are muted, but the can definitely looks red.

But it's not.

In reality, the only visible colors in this image are black, white and teal (or cyan).

from woahdude

Seriously, zoom in.

Trippy, right? There's a similar version that uses a more stripey pixelation:

And there's another version made out of black, white and yellow that makes the Coke can appear blue (negating the idea that our brain is automatically making the can red because it's the color our brain expects it to be).

Again, no blue in this image when you zoom in. There's only black, white and yellow.

So what exactly is going on here?

It's the complicated way our colors work and the way our eyes perceive and process them in our brains. Here's how one Reddit user explained it when someone claimed the white in the Coke can wasn't really white:

"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."

Another commenter verified that the white is, in fact, pure white. "The pixel color on the white is: #FFFFFF which means pure white. If there were any red in there we would see a variation on it like #FFFEFE. It is not a trick. It really is pure white," they wrote. "I too thought it might be a compression trick. Nope. Our brains just be weird."

Indeed, our brains do be weird.

Photographer and filmmaker Jared Bendis explained it in another way with a demonstration of the "Retinex effect," also known as color constancy. Essentially, because our eyes have to recognize color in varying kinds and amounts of light (otherwise how would we find food at different times of day), our brain is excellent at filling in blanks. How it works is rather complicated, so Bendis shows how it works using a photo of a bowl of fruit.

Our brains may be weird, but also very cool.