An afterimage is a visual illusion that occurs when you stare at an object for a prolonged period and then look away. The cells in your eyes, called photoreceptors, become overstimulated and temporarily retain the image, creating a ghostly impression of the original object. This effect can be seen in various colors, depending on the colors of the original image. Afterimages can be categorized into two types: positive and negative. A positive afterimage retains the same colors as the original image, while a negative afterimage displays the complementary colors. This phenomenon is a result of the way our visual system processes and adapts to light and color.