What Are The Colours Of The Rainbow?

Red, Orange, Yellow, Green, Blue, Indigo, Violet. In a double rainbow, the colours appear in opposite order in the arc, like a mirror image of one another. Rainbows have appeared prominently in myth and legend due to their extreme beauty and the wonder that surrounds them. In Greek Mythology it is believed that the messenger Iris used the rainbow as a path between Heaven and Earth. Hindu's believe that the rainbow is the bow of Indra, the God of Thunder and Lightning. Norwegians believe that the rainbow is a bridge between the homes of the gods and humans. A feature that has appeared in countless fairy tales over the years is the pot of gold at the end of the rainbow, this stems from the Irish Leprechaun's who were believed to have a crock of gold at the end of a rainbow that could never be reached. "Red and Yellow and Pink and Green, Orange and Purple and Blue, I can sing a rainbow, sing a rainbow, sing a rainbow too!"

The rainbow contains all the colours a human can see and a few we normally can't (like infra-red and ultra violet).
When reflected by raindrops, the different frequencies of Electromagnetic radiation from the sun (which make up visible light) are refracted at different angles. Lower frequency light (like Red) is refracted less, higher frequency light (like Blue) is refracted more. That's why the Red is always on the outside of the bow (unless you are lucky enough to see a second reflection of the bow where the higher frequencies are on the inside of the reflected bow).  However the distinct colours often used to describe a rainbow are as 'rucker' answered.

The colours are Red, Orange, Yellow, Green, Blue, Indigo, Violet.
You can remember this by.......( R-icard, of Y-ork, G-ave, B-attle, I-n, V-ain.

"rucker" left out indigo. The colours of the rainbow are ROYGBIV; Red, Orange, Yellow, Green, Blue, Indigo, Violet.

ROYGBIV red orange yellow green blue indigo violet and they are always in this order

The colors are red, orange, yellow, green, blue, violet.