The rainbow is a colorful visual and meteorological phenomenon in which the spectrum of light appears in the sky.
A rainbow is a series of concentric coloured arcs that may be seen when light from a distant source—most commonly the Sun—falls upon a collection of water drops—as in rain, spray, or fog. The rainbow is observed in the direction opposite to the Sun.
The coloured rays of the rainbow are caused by the refraction and internal reflection of light rays that enter the raindrop, each colour being bent through a slightly different angle. Hence, the composite colours of the incident light will be separated upon emerging from the drop.
The main colors of a rainbow are 7 and are as follows (from the outside to the inside):