Attention can influence the color that you perceive. In the moving case, one disk moves. This brings your attention to it, and you see the whole disk as having a uniform color.However, the middle region in fact always remains gray. This means that you sometimes see a gray region as part of a uniform blue, red, yellow or green object! (If you can”t see the animation you will need to download and install the Shockwave plugin).
This also works when you attend to a single figure in a static drawing. In the case of the static three disks, fixate the central fixation spot and then attend to one disk. The whole disk will appear to take on a uniform color. Attend to a different disk, and it will take on a different color, even though the middle overlap region always remains gray. The same goes for the case of overlapping rectangles. Attend, for example, to the blue rectangle, and the whole rectangle will appear blue. Now, attend to the other rectangle, and the whole rectangle will take on a different hue, even though the overlap region remains gray in every case.
Attentional modulation of perceived color
Dartmouth College, USA
(© 2012 Peter Tse)