What is the biblical meaning of the colors in the rainbow?

The colors are not specified in scripture, only the promise that God has set his bow into the sky or heavens. However, pure white light when traveling through a prism or a raindrop functioning as such, separates into visible wavelengths we see as colors. Roy G. Biv is not a Bible character, but a memory aid for red, orange, yellow, green, blue, indigo, violet--the most visible bands of a rainbow.