Learning Objectives - Color Phenomena
After Image - This we experience when we stare at the brightly illuminated TV, then shut our eyes and see a black rectangle in our field of vision. In the case of the TV screen, the contrast of a very bright light in a dark room, when you shut your eyes, your mind creates a black screen before your eyes, this After Image is based on 'value' or scale of light to dark.
A traditional After Image test done in theater studies class is to have students stair at a red dot on the projector screen for several moments, followed by a plain white screen. Most students will see a turquoise dot in the place of the red one.
In both examples what is happening?
Your mind wants balance, and when saturated with a single color it will produce the color opposite on the color wheel.
When your mind wants balance it dies interesting things. in our first example of after image your mind creates the opposite clor.
when presented with opposite colors, of the same intensity and brightness, if the two colors are next to each other; you will see the line vibrate, this effect was used intentionally for music posters n the 1960's, termed Psychedelic art due to the bright contrasting colors.
occasionally a speaker will inadvertently create this effect in a PowerPoint presentation, they may not notice, or know why, their audience avert their eyes. This example of your mind looking for balance involves unexpected results.
Activating a Neutral
In college, I took a card weaving class where we made a long strap to wear as a belt or guitar strap. The natural tones in fashion of the times made me choose a dark green and medium brown. The disappointing effect was Christmas colors instead of Knottingham forest. After weaving the yarns together in a 2" wide Aztec inspired pattern, the proximity of the colors created an effect of green and red. The 'neutral' brown had been influenced by the proximity to green and shifted its appearance to red. The lesson learned was to be careful when placing neutrals next to saturated colors, unless you want the neutral to shift toward the compliment, or opposite, of the stronger color.
Footnotes on this website are shown as a number following the text surrounded brackets, like this 
After Image Red Dot