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 fresh challenge is here to test your understanding of color perception. The ‘What’s My JND?’ test presents two color blocks, prompting you to click the dividing line between them. While the task seems simple at first, the difficulty escalates as the colors become more indistinguishable, making the task increasingly complex.

‘You see two colours. Click on the line between them. That’s it. It starts easy. It does not stay easy,’ the game’s instructions explain.

Each round, the colors converge until the test identifies your Just Noticeable Difference – the minimal change you can perceive. The game usually requires around 40 rounds, with an average score of 0.02.

Developed by software engineer Keith Cirkel, the game aims to explore the precision of color perception on screens. To begin, visit the game here and click the ‘Let’s go’ button. Each round, two color blocks appear on the screen, and your task is to locate the boundary.

Players share their experiences on social media, revealing how the test reveals individual differences. One user tweeted, ‘This is great fun. How good is your colour perception? What are the finest shades you can distinguish? Apparently I’m a bit special,’ while another joked, ‘Not bad considering I’m colourblind.’ A third noted, ‘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.’

‘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,’ a message reads if your score is low.

For those seeking a greater challenge, Hard Mode is available. In this version, nine squares are displayed, with eight matching and one different. The goal is to spot the unique square.

The human eye contains specialized structures that enable color vision. The pupil adjusts light intake, similar to a camera lens. Most animals have cones and rods in their eyes, which are photoreceptors in the retina. Cones detect color, while rods respond to low-light conditions, creating a grayscale perception.

Humans and many other species have three types of cones, each sensitive to different light wavelengths, covering the visible spectrum from red to blue (390 an 700 nm). Some animals, like many birds, possess four cones due to a mutation called tetrachromacy, allowing them to perceive ultraviolet light. These photoreceptors trigger electrical signals as they change shape, which are then carried to the brain via the optic nerve.

Signals from both optic nerves are processed by the brain at the optic chiasm, where