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 good is YOUR colour perception? Deceptively difficult test tasks you with finding the boundary between two shades – so, how far can you get?
But a new interactive challenge will have you doubting your understanding of color perception. The ‘What’s My JND?’ test presents two colors on the screen, prompting you to click the line separating them. At first, the colors are easily distinguishable—like grey and blue or brown and orange—but the difficulty increases as the game progresses, making the task progressively more challenging.
Each round, the colors become increasingly similar until the test identifies your Just Noticeable Difference (JND)—the minimal color change your eyes can detect. The game usually takes around 40 rounds, with the average score coming out as 0.02. To begin, visit the game here and click the ‘Let’s go’ button. You’ll be shown two color blocks, and your goal is to locate the boundary between them.
‘You see two colors. Click on the line between them. That’s it. It starts easy. It does not stay easy,’ the game’s instructions explain.
After each guess, you’ll be told if you’re correct or if your answer was significantly off. Early rounds feature stark contrasts—such as purple and blue—but as the game advances, the hues grow nearly indistinguishable. At the end, you’ll receive a score and a comparison to other players’ results.
If your score is below average, you might see a note stating, ‘Rough. But consider this—I once failed a color vision test due to fluorescent lighting. Environment plays a role. Try again in a dark room with maximum brightness, or don’t. I’m not your mum.’ For those who succeed, there’s a Hard Mode available. This version displays nine squares—eight with the same color and one that differs. Your goal is to identify the odd square out.
The game has sparked widespread interest, with players sharing their results on X. One user remarked, ‘This is great fun. How precise is your color vision? I’m quite remarkable, apparently.’ Another added, ‘Some were completely uniform to me. I had no clue. I tilted my screen in every direction to find a border, but still guessed.’ A third joked, ‘Not bad considering I’m colorblind.’
Science behind colour perception
The human eye contains complex structures that enable color vision. The pupil adjusts to regulate light intake, similar to a camera lens. Most animals, including humans, have both cones and rods as photoreceptors in their retinas. Cones detect color, while rods enhance low-light vision, contributing to grayscale perception.
Humans and many other species possess three types of cones, each responding to different light wavelengths. These allow for a broad spectrum of color vision, covering wavelengths between 390 and 700 nm—encompassing the visible light range from red to blue. In contrast, certain species like many birds have four cones, a trait known as tetrachromacy. This enables them to perceive light with unusually short wavelengths, such as ultraviolet (UV) light, expanding their color spectrum beyond humans’ capabilities.
When light interacts with these photoreceptors, they generate electrical signals as their shape changes. These signals travel to the brain through the optic nerve, where they are combined at the optic chiasm to compare the two visual inputs. This process reveals the intricate mechanisms behind how we and other animals interpret visual information.
