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?
A new test challenges your understanding of color perception by presenting pairs of hues and asking you to identify the subtle difference between them. At first glance, the task seems straightforward, but as the rounds advance, the colours grow increasingly similar, testing your ability to discern the faintest distinctions.
The game, titled ‘What’s My JND?’, displays two colour blocks and prompts you to click on the line separating them. Simple as it appears, the difficulty escalates rapidly, requiring precision and focus. According to the game’s instructions, ‘You see two colours. Click on the line between them. That’s it. It starts easy. It does not stay easy.’
Players are told that each round brings the shades closer together, eventually pinpointing their Just Noticeable Difference – the smallest colour change detectable by the human eye. The test typically spans 40 rounds, with an average score of 0.02, highlighting the precision needed to succeed.
Created by software engineer Keith Cirkel
The test was developed by software engineer Keith Cirkel, who aimed to explore the limits of colour accuracy on digital screens. To begin, visit the game and tap the ‘Let’s go’ button. Once started, participants are shown two colour blocks and must locate the dividing boundary.
After each attempt, the game reveals whether the guess was correct or significantly off. In the early stages, colours like grey and blue, or brown and orange, are clearly distinct. However, as the game progresses, the shades become nearly indistinguishable, demanding heightened attention.
Upon completion, players receive a score and a comparison to others who have taken the test. A low score might trigger a message like: ‘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.’
Hard Mode for advanced players
For those who master the test, a more challenging variant, Hard Mode, is available. This version presents nine squares – eight identical and one different – requiring players to spot the odd one out. The game has gained popularity, with users sharing their results on X.
One participant remarked, ‘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 added, ‘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.’ A third joked, ‘Not bad considering I’m colourblind.’
How the human eye perceives colour
Animals, including humans, possess complex eye structures that enable colour vision. The pupil adjusts to control light intake, similar to a camera lens. Most species have both cones and rods in their retinas, functioning as photoreceptors. Cones detect colour, while rods are sensitive to low-light conditions, allowing grey-scale vision.
Humans and many other animals have three types of cones, each responding to different light wavelengths. These cones cover the visible spectrum, from red to blue, with wavelengths between 390 and 700 nm. In contrast, some birds and insects have four cones due to a trait called tetrachromacy, enabling them to perceive ultraviolet light.
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. This is where the brain merges the visual data from both eyes, comparing them to create a coherent image.
