Munker-White Illusion

What do you see?

Blue and yellow stripes run across the picture. On the left, a block of pink bars replaces parts of the blue stripes; on the right, an identical block replaces parts of the yellow stripes. The two blocks look like different colours, one cooler and more purple, the other warmer and more orange. Press Reveal to remove the stripes: every pink bar is the same colour.

How it works

This is a colour version of White's illusion, and it is a famous puzzle because it runs against the simplest theory of contrast.

Look at the left block. Each pink bar sits in the path of a blue stripe, so its long top and bottom edges touch yellow stripes. If contrast depended only on bordering colours, the bars should look pushed away from yellow, toward blue-purple. On the right, the bars sit in yellow stripes with blue above and below, so they should be pushed away from blue, toward orange. In practice the shift tends to go the other way: the bars look more like the stripes that flank and interleave them, as though the colour of those stripes were spreading into the bars. This is called assimilation.

One explanation focuses on grouping. The visual system treats each bar as part of the stripe it is aligned with, because the bar continues that stripe's line and is bounded by the same edges. The short vertical edges at the ends of each bar form T-shaped junctions with the stripes. T-junctions are strong cues that one surface lies in front of or behind another. The brain uses them to decide which regions belong together and which comparisons count. The bar is compared mainly with the stripe it belongs to, so its colour is pushed away from that stripe and toward the colour of the flanking stripes.

Another explanation suggests that the brain sees the pink as lying behind a semi-transparent layer of stripes, and that colour is mixed accordingly. Both ideas emphasise that colour perception depends on how the brain parses a scene into surfaces and layers, not just on the light at each point.

The size of the stripes matters. When stripes are fine, assimilation usually dominates. When they are wider, contrast can take over. That is why the same principle can make colours look either more alike or more different depending on scale, a fact textile and print designers have used for centuries.

History

The grayscale version was described by Michael White in 1979, building on colour observations reported by Hans Munker in 1970. The colour form is often called the Munker-White illusion, and similar effects are used in modern colour science to test models of perception. This image was drawn for OpticalIllusions.com.

Try it

• Press Reveal to see the pink bars on a plain background.
• Squint or step back: the colour difference often grows.
• Cover the stripes around one block with paper.
• Use a colour picker on a downloaded copy to check the pink.

Written by K.R. for OpticalIllusions.com · Updated October 26, 2026. Illusion artwork © The Wizard Of Sales, LLC. Feel free to share a link; see our terms for reuse.