Color Test: Find the Different Color

How the color test works

Every level shows a grid of tiles in one color. One tile is a little brighter or a little darker than the others. Its hue and saturation are the same; only the brightness differs. Tap or click that tile and the next level starts in a new color.

You have three hearts. A wrong tap, or letting the time bar run out, costs one. The page then outlines the tile you were looking for and redraws the same level in new colors. When the hearts are gone the run ends, and the level you were on is your result. Your best level is kept in this browser.

Levels 1 to 10 use the same grids and brightness differences as our Short. The Short ends there. This page does not.

The brightness difference is measured as HSV value, the V of the hue, saturation and value color model, on a scale from 0 (black) to 1 (full brightness) (HSL and HSV). The base color of each board has a value between 0.6 and 0.82, and the odd tile sits above or below it by the amount in the table. After level 10 the remaining gap above the 0.008 floor shrinks by a fifth each level, so the difference gets closer to the floor without reaching it.

What makes it hard

• The difference approaches the smallest one you can notice. Psychophysics calls that the just-noticeable difference: the amount something has to change for the change to be detected at least half the time (Just-noticeable difference). Under Weber's law the just-noticeable difference is proportional to the size of the starting stimulus (Weber–Fechner law), so what counts is the size of a change relative to where it starts, not its absolute size. The early levels are far above that threshold. The late ones are close to it.
• There are more tiles to check. Level 1 has 4 tiles. Level 10 has 49, and the 8 by 8 boards have 64, in the same time or less. The tiles are smaller too, and the odd one can be anywhere, so you compare tiles that are far apart on the board, not side by side.
• The screen runs out of steps. A standard 8-bit screen shows 256 steps per color channel (Color depth). At level 10 the two colors are six or seven steps apart in their strongest channel. From about level 20 they are two or three steps apart. The page never draws two colors that round to the same value, so there is always a real difference on screen, but it can be smaller than your screen and eyes will show you.

What affects your score

The page sends your screen two colors. What reaches your eyes depends on the screen and the room, so a level is a score for you on this screen today, not a fixed measure.

• Night mode and blue-light filters. Night Shift and similar modes move the display's colors toward the warmer end of the spectrum (Apple). Every tile changes with them, so you are no longer comparing the colors the page drew.
• True Tone and other automatic adjustments. True Tone adjusts the color and intensity of the display to match the light around you (Apple). Auto-brightness can also change the picture in the middle of a run.
• Screen brightness and glare. A dim screen, or a bright room reflecting off the glass, makes small differences harder to see.
• The screen itself. Screens differ in how they show neighboring shades, and on some the colors shift when you look from the side. Look straight at the screen, and compare scores only when they were made on the same device.
• Tile size and tired eyes. The boards are smaller on a phone than on a monitor. If your eyes feel tired, take a short break between runs.

Not a color vision test

This game changes only brightness. Color vision deficiency, often called color blindness, is about telling certain colors apart: the most common type makes it hard to tell the difference between red and green (National Eye Institute). Eye doctors check for it with a color plate test (National Eye Institute). A high or low level here says nothing about that. If you have questions about your color vision, ask an eye care professional.

Color test FAQ

Is this a color blindness test?

No. Only the brightness of one tile changes here, never the hue. Color vision deficiency is about telling certain colors apart, most often red and green, and an eye doctor checks it with a color plate test. Your level on this page says nothing about it.

How many people reach level 10?

We do not know, so this page gives no figure. It does not collect players' scores, and the line in the Short's title is a hook, not a measurement. Level 10 is simply where the Short ends.

Why can't I see any difference at the high levels?

Past level 10 the difference keeps shrinking. From about level 20 the two colors are only two or three steps apart, out of the 256 steps a standard 8-bit screen has per color channel. They are never identical, but screen settings and room light can hide a gap that small.

Do screen brightness, night mode or True Tone change the result?

Yes. Night mode and blue-light filters shift every color toward warmer tones, True Tone adjusts the display's color and intensity to the light around you, and a dim screen or glare makes small differences harder to see. Compare scores only when they were made on the same screen with the same settings.

What happens after level 10?

The test keeps going. Level 11 is still 7 by 7, and from level 12 the grid is 8 by 8. The brightness difference keeps shrinking toward a floor of 0.008, and the time limit drops by half a second per level until it is 6 seconds from level 18. These levels are labeled BEYOND.

Is my score saved or sent anywhere?

Your best level is saved in this browser's local storage only, so it stays on this device. For usage statistics the page sends Google Analytics two events with no personal details: that a run started, and the level a run ended on.

Sources

1. Wikipedia. Just-noticeable difference. en.wikipedia.org/wiki/Just-noticeable_difference
2. Wikipedia. Weber–Fechner law. en.wikipedia.org/wiki/Weber–Fechner_law
3. Wikipedia. HSL and HSV. en.wikipedia.org/wiki/HSL_and_HSV
4. Wikipedia. Color depth. en.wikipedia.org/wiki/Color_depth
5. National Eye Institute. Color Blindness. nei.nih.gov
6. National Eye Institute. Testing for Color Vision Deficiency. nei.nih.gov
7. Apple Support. Use Night Shift on your iPhone, iPad, and iPod touch. support.apple.com/en-us/118583
8. Apple Support. Use True Tone on Mac. support.apple.com/en-us/102147

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