Sciencetech

How good is YOUR colour perception? Deceptively difficult test tasks you with finding the boundary between two shades – so, how far can you get?

Lisa Lopez March 27, 2026

Table of Contents

How accurate is your ability to distinguish colors? A tricky test challenges you to spot subtle differences

A recent interactive game is designed to push the limits of your visual acuity, testing whether you can discern the faintest variations in color.

Gameplay mechanics

Players are presented with two hues on the screen and tasked with identifying the boundary between them by clicking the dividing line. While the initial rounds are straightforward, the difficulty escalates rapidly as the color pairs grow increasingly similar.

‘The task seems simple at first—two colors, a line to click. But as the game progresses, the challenge intensifies, demanding a sharp eye to detect the most minute distinctions.’

Understanding the test

Developed by software engineer Keith Cirkel, the game measures your Just Noticeable Difference (JND), which refers to the smallest perceptible change in color that the human eye can detect. This typically requires around 40 rounds, with the average performance falling near 0.02.

To begin, navigate to the game’s website and select the ‘Let’s go’ button. Each round displays two blocks of color, requiring you to locate the transition point. Feedback is provided instantly, highlighting whether your choice was precise or significantly off.

User experiences

‘I once failed a color test due to fluorescent lighting. Environment plays a role, so try testing in a dimly lit room with maximum brightness—or ignore it entirely. I’m not your mother.’

Players have shared mixed reactions to the game’s difficulty. Some found it surprisingly challenging, while others boasted about surpassing expected human capabilities. One participant noted, ‘Not bad considering I’m colorblind,’ underscoring the test’s ability to reveal hidden perceptual strengths.

Scientific insight

Human eyes contain specialized cells called cones that detect color, while rods register light intensity. Most species, including humans, have three types of cones sensitive to different light wavelengths, enabling color perception across the visible spectrum (390–700 nm). Birds, however, may possess four cone types, allowing them to perceive ultraviolet light and distinguish finer color gradations.

When light interacts with these photoreceptors, it generates electrical signals transmitted to the brain via the optic nerve. The brain then merges signals from both eyes at the optic chiasm, comparing the inputs to form a cohesive visual experience.

Additional challenges

For those seeking a harder version, Cirkel has introduced a Hard Mode. In this variant, nine squares are displayed—eight identical and one unique. The goal is to pinpoint the odd square, testing your ability to detect even the subtlest chromatic shifts.

The game has sparked widespread interest, with players discussing their scores on social media. One noted, ‘This is great fun. How good is your color perception? What are the finest shades you can distinguish? Apparently I’m a bit special.’ Another added, ‘Some were completely uniform to me. I had to tilt my screen in all directions to find a border, but still guessed.’