What do you know about the rainbow colours?
The rainbow colours were first classified by Sir Isaac Newton in 1670-1672. At that period of time he was lecturing on optics and working on his theory of colours.
The most commonly cited and remembered sequence of the rainbow colours is Newton's sevenfold red, orange, yellow, green, blue, indigo and violet.
Originally Newton named only five primary colours: red, yellow, green, blue and violet.
Later he added orange and indigo. Seven colours were taken as an analogy to the number of notes in a musical scale.