We all know that Newton wrote about the colour spectrum having seven colours. As a child I wrote the mnemonic – Richard Of York Gave Battle in Vain. The sentence makes reference to Richard III, an English king who was defeated by Henry VII in 1485 at the battle of Bosworth. In order to avoid reference to this defeat, people from Yorkshire developed the alternative Rowntrees Of York Gave Best In Value, apparently. Rowntrees was a chocolate factory formed in York in 1862 (exactly one hundred years before I was born).

When I was young I naively thought that everyone would know the Richard of York line. I was surprised, later in life to learn that in the USA a different mnemonic is normally used: Roy G Biv (the name of a person). I find this American mnemonic a little bizarre to be honest; are there really people whose surname is Biv? If your surname is Biv, or you know someone called Biv, please comment below. Only recently I came across a small rhyme that goes:

Red for the rainbow, orange too.
Yellow says, ‘how do you do’.
Green is the next one, green for go.
Then comes blue and indigo.
Number seven, we must not forget, is pretty violet.

Since children learn these mnemonics from an early age most people never question whether there really are seven colours in the spectrum despite the fact that we often see the spectrum in the form of a rainbow in the sky. However, if most people look closely at the spectrum they will likely state that they can only discriminate between six bands of colour; that indigo and violet are really one colour band. So why is it that we teach children that there are seven colours in the rainbow?