A negative afterimage occurs when you stare at a bright image for a prolonged period and then look away at a neutral background. The intense light causes the photoreceptors in your eyes to become temporarily desensitized. When you shift your gaze, you may see a reversed color version of the original image, where bright areas appear dark and vice versa. This phenomenon is a result of the way our eyes and brain process visual information. The retina contains cells called cones that detect color, and after overstimulation, they can produce a complementary color effect. This is why the afterimage appears as a negative of the original scene.