Are the Strawberries Red?

A new image on the web has raised lots of curiosity about the way that colour vision works. Although the image shown has no red pixels, it is perceived as having red strawberries. The explanation for this is that the brain tends to assume that the light illuminating the image is ‘white’. while in the image it is actually a very light blue. To compensate for this, the brain effectively ‘subtracts’ blue from the grey on the strawberries, and that leaves red! We also expect strawberries to be red.

For more coverage, including some variations, check the BBC website