Is this fire truck really red? What a popular optical illusion reveals about your brain
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We’ve all seen it—the classic bright red fire truck, bold and unmistakable, often among the easiest vehicles to recognize no matter where you are.
For most of us, that vivid red color is as familiar as the sound of the siren.
It’s part of what makes fire trucks so instantly identifiable.
But what if that red fire truck wasn’t actually red? Would you believe your own eyes—or your brain?
That’s exactly the kind of question being raised by a curious photo making the rounds online.
In the image, a fire truck that seems undeniably red isn’t red at all—and it’s leaving many viewers second-guessing what they thought they knew about color and perception.
The illusion was shared by Dr. Dean Jackson, a biologist and science communicator who often explains complex topics in simple, visual ways. I
What’s going on in this illusion?
It starts with a seemingly ordinary image of a fire truck parked on a road.
It looks red, just like you’d expect.
But then a cyan filter—essentially a transparent blue-green layer—is placed over the image.
Dr. Jackson asks viewers to take another look.
Even with the filter applied, most people still say the truck is red.
But in reality, it’s actually gray.
How is that possible?
According to Dr. Jackson, “Red light cannot pass through a cyan filter, it just can’t. So now there is no red light in that picture, I can promise you. And yet your brain is still telling you that it’s red.”
Also read: Unlock the secret to melt away stress with this simple color walk technique
Why your brain is filling in the blanks
This effect has everything to do with how we process visual information.
Our eyes contain light-sensitive cells called cones that help us perceive color.
There are three types of cones, each tuned to red, green, or blue light.
When a cyan filter blocks out red, the only light reaching your eyes is a combination of green and blue—yet somehow, your brain still sees red.
That’s because of something called color constancy, a natural tendency of our brains to maintain familiar colors even when the lighting or filters around them change.
Since our brains are so used to seeing fire trucks as red, they fill in that color even when it isn’t present in the image.
To show just how powerful this effect is, Dr. Jackson moves a gray square across the image.
When the square passes over the truck, it appears to “turn red”—even though it’s the exact same color throughout.
“It’s your brain doing it,” he says. “The brain is a remarkable organ.”
Source: TikTok / @beatonthebeeb
Also read: Passenger stunned by 'alien' optical illusion—See it to believe it!
Why this illusion feels so real
The video has captured widespread interest, with many people commenting on how real the “red” appears, even though it’s not there at all.
Some say the square changes color right before their eyes, while others notice it only looks red when placed over the truck, not when it’s on its own.
These reactions are classic examples of how optical illusions reveal gaps between what we see and what we believe we’re seeing.
What this tells us about perception
Optical illusions like this one aren’t just visual tricks—they’re windows into how the human brain works.
Just like “The Dress” debate from years ago (was it blue and black, or white and gold?), this fire truck illusion reminds us that our brains interpret the world based on memory, context, and expectation—not just raw visual input.
So even when the physical light in an image changes, your brain may still interpret what it thinks you should see.
It’s one of the reasons why a white shirt still looks white whether you’re indoors or out, even if the actual light bouncing off the fabric is very different.
At the end of the day, this illusion is a simple, fun way to see how perception works.
It reminds us not to take everything we see at face value—because sometimes, our minds are working behind the scenes to fill in gaps we don’t even notice.
And while it might not change how you see every fire truck from now on, it’s a fascinating example of how science can challenge the way we experience the everyday world.
Read next: Think you have sharp eyes? Most people miss at least 3 ducks in this tricky puzzle
Have you ever been fooled by an optical illusion? Do you remember the “The Dress” debate or another moment when your eyes and brain didn’t quite agree? We’d love to hear your stories—share your favorites in the comments and keep the conversation going!
For most of us, that vivid red color is as familiar as the sound of the siren.
It’s part of what makes fire trucks so instantly identifiable.
But what if that red fire truck wasn’t actually red? Would you believe your own eyes—or your brain?
That’s exactly the kind of question being raised by a curious photo making the rounds online.
In the image, a fire truck that seems undeniably red isn’t red at all—and it’s leaving many viewers second-guessing what they thought they knew about color and perception.
The illusion was shared by Dr. Dean Jackson, a biologist and science communicator who often explains complex topics in simple, visual ways. I
An optical illusion is challenging how we see—and what we think we see. Image Source: Pexels / Alexander Hamilton.
What’s going on in this illusion?
It starts with a seemingly ordinary image of a fire truck parked on a road.
It looks red, just like you’d expect.
But then a cyan filter—essentially a transparent blue-green layer—is placed over the image.
Dr. Jackson asks viewers to take another look.
Even with the filter applied, most people still say the truck is red.
But in reality, it’s actually gray.
How is that possible?
According to Dr. Jackson, “Red light cannot pass through a cyan filter, it just can’t. So now there is no red light in that picture, I can promise you. And yet your brain is still telling you that it’s red.”
Also read: Unlock the secret to melt away stress with this simple color walk technique
Why your brain is filling in the blanks
This effect has everything to do with how we process visual information.
Our eyes contain light-sensitive cells called cones that help us perceive color.
There are three types of cones, each tuned to red, green, or blue light.
When a cyan filter blocks out red, the only light reaching your eyes is a combination of green and blue—yet somehow, your brain still sees red.
That’s because of something called color constancy, a natural tendency of our brains to maintain familiar colors even when the lighting or filters around them change.
Since our brains are so used to seeing fire trucks as red, they fill in that color even when it isn’t present in the image.
To show just how powerful this effect is, Dr. Jackson moves a gray square across the image.
When the square passes over the truck, it appears to “turn red”—even though it’s the exact same color throughout.
“It’s your brain doing it,” he says. “The brain is a remarkable organ.”
Source: TikTok / @beatonthebeeb
Also read: Passenger stunned by 'alien' optical illusion—See it to believe it!
Why this illusion feels so real
The video has captured widespread interest, with many people commenting on how real the “red” appears, even though it’s not there at all.
Some say the square changes color right before their eyes, while others notice it only looks red when placed over the truck, not when it’s on its own.
These reactions are classic examples of how optical illusions reveal gaps between what we see and what we believe we’re seeing.
What this tells us about perception
Optical illusions like this one aren’t just visual tricks—they’re windows into how the human brain works.
Just like “The Dress” debate from years ago (was it blue and black, or white and gold?), this fire truck illusion reminds us that our brains interpret the world based on memory, context, and expectation—not just raw visual input.
So even when the physical light in an image changes, your brain may still interpret what it thinks you should see.
It’s one of the reasons why a white shirt still looks white whether you’re indoors or out, even if the actual light bouncing off the fabric is very different.
At the end of the day, this illusion is a simple, fun way to see how perception works.
It reminds us not to take everything we see at face value—because sometimes, our minds are working behind the scenes to fill in gaps we don’t even notice.
And while it might not change how you see every fire truck from now on, it’s a fascinating example of how science can challenge the way we experience the everyday world.
Read next: Think you have sharp eyes? Most people miss at least 3 ducks in this tricky puzzle
Have you ever been fooled by an optical illusion? Do you remember the “The Dress” debate or another moment when your eyes and brain didn’t quite agree? We’d love to hear your stories—share your favorites in the comments and keep the conversation going!
