






For example, in this classic shadow illusion by Edward H. Adelson, A and B are the exact same shade of gray:





There are actually only three colors in this image -- white, red and green (sorry, color blind people). Also via BrainDen.

The blue and yellow border around this image by Jochen Burghardt creates the illusion that it is pale yellow, instead of white:


The same principle is at work in this motion illusion by Japanes professor Akiyoshi Kitaoka called "Rotating Snakes." As you stare at the image, the circles will appear to turn.

If you stare at the center of this illusion by Jeremy Hinton, you will eventually see a revolving green circle. When the lilac disappears, the adaptation of rods and cones in the retina leaves a green afterimage.

In Pinna's illusory intertwining effect, shown here in an illustration by Jochen Burghardt, colors give the illusion that circles are intertwining (they are actually concentric).

But probably the best illusion on the subject of the dress is by Randall Munroe of Xkcd, who immortalized the debate in an optical illusion cartoon form.