An optical illusion that popped up on Reddit recently has kicked off a lively debate about a surprisingly tricky question: Are these dots blue, or are they purple?
The image itself uses a vivid shade of electric violet (hex code #6600ff). But a lot of people swear they see something different.
Some folks only see the dot they’re staring at as purple, while the others around it seem to turn blue—or just fade away. Others say tweaking their device’s screen, like turning on a phone’s eye comfort mode, changes the whole effect.
It’s a weird little puzzle, but it actually hints at some deeper stuff about how we see color—especially purple, which is a bit of a troublemaker.
The Curious Case of Purple
Colors like red, green, and blue are tied directly to specific wavelengths of light. Purple, though, isn’t so straightforward.
Scientists call it a non-spectral color because there’s no single wavelength for purple. Our brains have to mix signals from our eyes to create that sensation.
How the Brain Synthesizes Purple
We see using three kinds of cones in our retinas: L-cones for long wavelengths, M-cones for medium, and S-cones for short.
Purple shows up when L-cones and S-cones fire together, but without much action from the M-cones. It’s a delicate process, and that’s why purple can feel so unstable or shifty.
The Optical Illusion Explained
The Reddit illusion actually comes from a study looking into why purple is so tricky for our eyes. Researcher Hinnerk Schulz-Hildebrandt and his team pinpointed three main reasons:
- Color contrast effects – The colors around the dots can fool our brains, making purple look blue, especially if you’re not looking straight at them.
- Neurological synthesis of purple – Since our brains have to “build” purple from mixed signals, even tiny changes in how we look at it can make it seem totally different.
- Biological distribution of cones – S-cones (which help us see purple) aren’t in the very center of our vision, so purple pops most in the exact spot you’re focusing on.
The Role of Individual Physiology
That lack of S-cones right in the middle of your vision explains why only the dot you’re staring at looks truly purple. The rest might just fade or look blue.
Stuff like your screen’s settings or the room’s lighting can make your experience totally unique, too.
Why Purple Is Unstable
Our sense of purple depends on a pretty fragile mix of signals in the brain. Since purple isn’t a “real” wavelength, tiny changes in how our cones get triggered can flip it from purple to blue or something else entirely.
Other factors, like your device’s display or what colors are nearby, just add to the weirdness. Purple can be a bit of a chameleon.
Implications for Color Science
This illusion isn’t just a fun trick. It’s a real-world example of how our biology and perception interact in ways that aren’t always obvious.
Learning how we put together non-spectral colors like purple could matter a lot in digital imaging, ergonomics, or even art—anywhere color relationships really matter.
Seeing Beyond the Illusion
The electric violet dots remind us that seeing isn’t always believing. Our brains don’t just record what’s there—they build a version of reality, using whatever info they’ve got.
With purple, that construction is so wobbly that a single, unchanging image can look wildly different to different people. Kind of mind-bending, honestly.
A Lesson in Visual Chemistry
From a scientific standpoint, this illusion shows that colors aren’t built into objects. They’re perceptual phenomena that come from light and how our biology handles it.
How we see these phenomena depends on a careful mix of signals from our photoreceptors and neural processing. Even the technology we use to look at the world plays a part.
Next time you see purple—or think you do—remember your perception is a wild collaboration between photons, retinal cells, and brain chemistry.
Here is the source article for this story: Dotty optical illusion shows purple is different from other colours