I did a second-grade science-fair project on this phenomenon. It’s an after-image-type optical illusion. Here’s what I remember about it: When you stare at the pink dots, the cells on your retina that respond to pink start to get tired and then fire less. Then, when a pink dot is removed, your eyes deceive you and you think you see pink’s complementary color, light green, in its place. Because the cells that report the presence of pink also report the absence of green simultaneously, your brain misinterprets the decrease in activity in your fatigued pink-receptor cells as the presence of green.

You can create the effect by staring at something brightly-colored like a Post-it or a highlighter for 30 seconds and then switching your gaze to a white sheet of paper. You should see the same shape in the opposite color. Fun! Get back to work.