Why do rainbows occur? They occur while it is raining or just after a storm. It appears in the sky directly opposite to the sun. So you must stand with your back to the sun to see it. A rainbow is made when the sun’s rays are reflected through raindrops, which are prismatic in form. This light is reflected back to us and seems like an arch made of seven different colours. Actually, although the light we see from the sun appears white, it is really made up of waves of colours that get separated when bent.