What is the order of colours in a rainbow, from the outside to the inside?

The order of colours in a rainbow, from the outside to the inside is: red, orange, yellow, green, blue, indigo and violet.

Explanation

The band of seven colours formed on a white screen, when a beam of white light is passed through a triangular glass prism is called spectrum of white. 

The seven colours of the spectrum are denoted by the word $VIBGYOR$ (from bottom to top), where $V$ stands for Violet, $I$ stands for Indigo, $B$ stands for Blue, $G$ stands for Green, $Y$ stands for Yellow, $O$ stands for Orange, and $R$ stands for Red.