I had a pair of red sunglasses back when colored lenses were cool (or at least back when I thought they were). But I couldn’t wear them when driving because they make traffic lights look broken. The green light appears burned out and it’s very distracting, so I saved them for the beach or indoor poetry readings instead. That same optical illusion is on display in the TikTok video below and it’s blowing people’s minds and dividing the internet. Does the red light still look red to you, or do you believe it’s actually gray?
Instead of a straight green filter, the traffic light is covered with cyan, which is blue-green. Cyan is nearly, but not completely, opposite from red on the color wheel. That means it blocks out the red but leaves behind a gray that still looks reddish to many people. That’s because of the context, our eyes and brains know that top light is red, so it still looks red. The illusion works whether you call them traffic lights, stoplights, or even robots, as they do in some parts of the world.
We saw this brain teaser thanks to Boing Boing. The article also shows a plate of strawberries with a cyan filter, but they still look quite red as well. If you want to put your brain through the ringer, Dean Jackson, a BBC host, shares many other optical illusions on his TikTok channel.
We love a good optical illusion, especially when cute animals like otters get in on the mind-bending fun as well. There are even scientists who study color in optical illusions to explore the connection between our eyes and the areas of the brain that process what we see. Whether or not you understand the science behind it, tricking our eyes into seeing things that aren’t there—like motion in works of art like The Starry Night—is undoubtedly fun.
Melissa is Nerdist’s science & technology staff writer. She also moderates “science of” panels at conventions and co-hosts Star Warsologies, a podcast about science and Star Wars. Follow her on Twitter @melissatruth.