So rainbows are basically freaking amazing ^.^ They are colorful and purty and colorful. There are 7 basic colors in a rainbow, red, orange, yellow, green, blue, indigo, and violet. Rainbows are mainly seen after rain showers. ;3

Rainbows are caused by light refracting off moisture drops in the air and the colors are caused by the fact different colors ( wavelengths) of light are refracted by different amounts. 

A rainbow is caused by light being refracted from tiny water droplets in the air. When it rains or there is a mist all the tiny water droplets refract sunlight like a prism (a triangular piece of glass). Refracted means the light of the sun is split up into its basic colors. Sunlight is actually a combination of Red, Orange, Yellow, Green, Blue, Indigo, Purple. When these colors are all combined they look white, which is what sunlight usually looks like to us. There is also other light energy from the sun like Infrared which makes sunlight hot and Ultra Violet which makes you tan or sunburn. You can not see Infrared or Ultra Violet because the human eye is not designed to see them. But some creatures can.  To see a rainbow, there should be a little rain or moisture in the sky and the Sun should be shining behind you.