To learn how color vision works, researchers sent a laser pulse to individual cone cells in the eyes of two men. Colored dots indicate the color of light-detecting pigment in each cone cell. A crosshair shows where a laser flash will appear. After cells were stimulated with the laser, the men indicated what color they perceived. Many red or green cone cells send a white signal instead of a color signal to the brain, the researchers found. Cells surrounded by cones of a different color were more