Focus on the middle stripe of this flag for 20-30 seconds. Try not to blink. Then move your mouse so that the cursor moves onto the flag. This will the background to go white and you should see the flag of the USA in the correct colors. Sometimes it helps to blink once or twice after the background changes.
What's Happening: in the retina of your eyes, there are 3 types of color receptors (cones) that are most sensitive to either red, blue or green. When you stare at a particular color for too long, these receptors get "tired" or "fatigued.". After looking at the flag with the strange colors, your receptors that are tired do not work as well. Therefore, the information from all of the different color receptors is not in balance. Therefore, you see different color "afterimages"...in this case I have used the "mirror" colors so you see the proper colors in the afterimage. You can also see that your vision quickly returns to normal since the afterimage does not last for more than about 5 seconds.