The color indigo falls in between blue and violet in a rainbow. The full order for the colors of the rainbow is red, orange, yellow, green, blue, indigo and violet.
There are many mnemonic techniques for remembering the order of the colors of the rainbow. The most popular include "Roy G. Biv" and "Richard of York gave battle in vain."
A rainbow is a large arc of colour, seen in the sky where there is both sunlight and rain. A rainbow occurs because rain droplets break up the light from the sun into seven visible colors. Rainbows are full circles of light, but people see them as arcs because they are viewing them from the ground.