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 ability to discern colors? A tricky test challenges you to identify the subtle line between two shades
A fresh interactive challenge has emerged, pushing participants to reconsider their understanding of color recognition. This test, titled ‘What’s My JND?’, presents users with two color blocks and invites them to click the dividing line between them. While the task seems straightforward, the game gradually intensifies, making the distinction between colors increasingly difficult to spot.
The game’s instructions outline: ‘You see two colors. Click on the line between them. That’s it. It starts easy. It does not stay easy.’ As the rounds progress, the colors converge, demanding sharper visual discrimination. The ultimate goal is to determine your Just Noticeable Difference—the smallest perceptible shift in hue that your eyes can detect.
‘Each round the colors get closer together until we find your Just Noticeable Difference – the smallest colour change you can actually see.’
The test typically spans 40 rounds, with an average completion score of 0.02. To engage, visit the game and initiate by tapping the ‘Let’s go’ button. In every round, two color blocks appear on the screen, and your task is to locate the boundary. After each attempt, the system provides feedback on your accuracy.
In the initial stages, colors like grey and blue, or brown and orange, are clearly distinct. However, as the game advances, the hues become nearly indistinguishable. At the end, your score is displayed, along with a comparison to other players’ results.
‘Rough. But look, I once failed a colour 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.’
For those seeking a greater challenge, the creator has also developed a Hard Mode. In this version, nine squares are shown—eight identical and one different. The objective is to spot the unique shade among them.
Player reactions and the science of color perception
Players have shared their experiences online, with some highlighting the difficulty of the task. One user noted: ‘This is great fun. How good is your colour perception? What are the finest shades you can distinguish? Apparently I’m a bit special.’ Another remarked: ‘Some were just completely uniform to me. I had no idea. Had to keep tilting my screen all ways to try to spot a border but still ended up guessing.’
‘Not bad considering I’m colourblind.’
Keith Cirkel, a software engineer, designed the game to explore how precise color perception can be on digital screens. His curiosity centered on identifying the threshold for accurate color distinction. The test leverages the human eye’s complex structures, such as cones and rods, which function as photoreceptors in the retina. Cones enable color vision, while rods enhance low-light sensitivity, facilitating grayscale perception between black and white.
Humans and other animals typically have three types of cones, each responding to different light wavelengths. This trio allows for a broad spectrum of visible colors, ranging from red to blue, with wavelengths between 390 and 700 nm. Some species, like many birds, possess four cones, a trait known as tetrachromacy. This mutation enables the detection of light at shorter wavelengths, including ultraviolet.
When light interacts with photoreceptors, it triggers electrical signals as the cells alter shape. These signals travel to the brain through the optic nerve, where they are processed. At the optic chiasm, signals from both eyes merge, allowing the brain to compare the two visual inputs and construct a coherent image.