Munker Colors

What is happening

What look like vertical columns are actually a stack of small green rectangles rather than a single solid fill. See whether the color impression changes depending on whether you compare individual fragments side by side, or take in each whole column as a single unit. The background is only two colors: yellow and blue.

Why it looks that way

Colors inside thin stripes can visually blend with the surrounding stripe color. On the left and right, the green replaces opposite-colored stripes, so its relationship to the remaining stripes differs. This is related to color assimilation, a phenomenon that a simple opposite-color contrast alone doesn’t explain.

How to check

Removing the context leaves only the identical green fragments. Revealing the answer draws a band in that same green connecting the two sides. Screen color settings and scaling change how much blending occurs, so compare at a size where the fragments are still clearly legible.

Try a related illusion

For reference: Michael Bach’s explanation. The figure here is an original implementation for this site.

First described

After Hans Munker, 1970

Part of the same lineage as the color assimilation effect Wilhelm von Bezold reported in 1874, and closely related to White's illusion.

See it in the timeline