How good is YOUR colour perception? Deceptively difficult test tasks you with finding the boundary between two shades – so, how far can you get?
How precise is your color vision? A tricky test reveals the limits of your ability to distinguish shades
Keith Cirkel, a software developer, has crafted a challenge that pushes the boundaries of color recognition. The game, titled ‘What’s My JND?’, presents players with two hues and asks them to identify the dividing line between them.
While the task seems straightforward at first, the difficulty escalates rapidly. As the game progresses, the colors grow increasingly similar, making the task of spotting the boundary more complex. The instructions state, “You see two colors. Click on the line between them. That’s it. It starts easy. It does not stay easy.”
Each round tests your perception by narrowing the gap between hues until it reaches your Just Noticeable Difference (JND)—the minimal change you can detect. The process typically involves 40 iterations, with most participants achieving a score of 0.02.
Players can access the game via a provided link and begin by tapping the “Let’s go” button. The interface displays two color blocks, and the goal is to locate the boundary between them. After each attempt, the game informs you if your guess was correct or not.
Initially, the colors are distinct—such as grey and blue, or brown and orange. However, as the game advances, the shades converge, demanding sharper visual discrimination. At the end, your score is revealed, along with comparisons to other players’ results.
‘This is great fun. How good is your color perception? What are the finest shades you can distinguish? Apparently I’m a bit special,’ one user tweeted.
If you excel in the basic version, you may be greeted with a message like: “Genuinely remarkable. You sailed past the theoretical human limit like it owed you money. I’d accuse you of cheating but I don’t actually know how you’d cheat at this.”
For those seeking a greater challenge, the creator has introduced a Hard Mode. In this version, nine squares are displayed—eight identical and one unique. Your task is to detect the outlier.
‘Rough. But look, I once failed a color vision test because the room had fluorescent lighting. Environment matters. Try again in a dark room with your brightness cranked. Or don’t. I’m not your mum.’
The game has sparked widespread engagement, with players sharing their experiences on social media. Some described the test as uniformly challenging, requiring them to adjust their screens to spot subtle differences. Others joked about their colorblindness, noting, “Not bad considering I’m colorblind.”
Understanding the science behind color perception
Color vision is made possible by intricate structures in the eyes. The pupil regulates light intake, similar to a camera lens, while photoreceptors in the retina process visual data. Most animals, including humans, rely on cones and rods for this function.
Cones are responsible for color detection, while rods excel in low-light conditions, enabling grayscale vision. Humans possess three types of cones, each sensitive to different wavelengths of light, covering the visible spectrum from red to blue.
Other species, such as many birds, have an additional type of cone, a trait known as tetrachromacy. This allows them to perceive ultraviolet light, expanding their color spectrum beyond human capabilities.
When light hits the photoreceptors, it triggers electrical signals as the cells change shape. These signals travel through the optic nerve to the brain, where they are processed at the optic chiasm—a junction that combines visual data from both eyes.
