Here's an optical illusion GIF that I created to demonstrate color afterimages. Bring your face close, turn up your screen brightness, and stare at the center of the grid.
(Direct link if the GIF doesn't work) Every three seconds it switches from bright colors to neutral gray. The afterimage effect tinges the gray squares with the complementary (or opposite) color. The effect doesn't last long because the stimulus is short and the color receptors don't have much time to get depleted.
(Video link) The same principle applies to this video, where a color afterimage infuses a black and white photo with the appearance of natural color.
To get the best effect, watch the video at full screen size and stare for the duration of video at the dot in the center. When it switches over to the photo, keep looking at the center. Your retinas have been primed with a seemingly random (but really a complementary) color pattern for a longer period of time. The colors are more stable this time because the depletion is more dramatic.