Colour difference game
One tile is different. Find it.
Every square is the same colour except one. Tap the odd one. Each round the grid gets bigger and the difference gets smaller. You have sixty seconds.
Press start. A wrong tap costs three seconds.
This is a game, not a colour-vision test. Screens, brightness and night modes all change how close two shades look.
Free tool from Focus and Screen Time
How it works
Each round picks a random colour and makes one tile a little lighter or darker than the rest. Early on the gap is obvious. As your score climbs the two shades move closer together and the grid grows from four tiles to sixty-four, so you are searching more squares for a smaller difference.
Why it gets hard
Your eyes are far better at spotting a difference when two colours sit side by side than when they are apart. On a big grid the odd tile may be nowhere near the centre of your gaze, where colour vision is weaker. That is why sweeping your eyes across the grid works better than staring at the middle.
Tips
- Turn the brightness up and switch off night mode or any blue-light filter. They squash the differences you are hunting.
- Relax your focus. Look at the whole grid slightly out of focus; the odd tile often pops as a faint patch.
- Do not guess. A wrong tap costs three seconds, more than a second look does.
- Take breaks. Staring at one colour tires the receptors that see it, and everything starts to look the same.
What a score does and does not tell you
A higher score means you found small differences quickly on this screen today. It does not diagnose anything. If you have real concerns about colour vision, an optometrist can test it properly with standard plates under controlled lighting.
Questions people ask
What is a color difference test?
It is a game where every tile is the same colour except one that is slightly lighter or darker. You find the odd tile as the grid grows and the difference shrinks.
What is a good score?
There is no standard. Scores depend heavily on your screen and its brightness, so compare with your own earlier runs or with a friend on the same device.
Can this test tell if I am colour blind?
No. It is a game. Colour-vision deficiency is checked by an optometrist using standard tests under controlled conditions.
Curious how the rest of your attention holds up?
Attention Age: Focus Test is an iPhone app built around a five-minute test with five category scores. Its listing says the three core practice drills, weekly results and a 10- or 25-minute timer are free.
Get Attention Age on the App StoreOptional auto-renewing Pro adds drills, circuits and longer timers. Scores describe performance in its own games; it is not a medical or diagnostic test. iOS 18 or later.
Honest Little Apps publishes both Attention Age and this page. This is a separate browser tool and does not sync with the app. App details checked November 10, 2026.
On a computer? Open it on your iPhone
