Latest in the time-honoured tradition of politicians exposing their woeful ignorance of just about everything is UK schools secretary, the appropriately named Ed Balls. In a presentation to the
Children, Schools and Families Committee of the UK Parliament, Mr Balls categorised the colours of the rainbow as «red and yellow and pink and green, purple and orange and blue». I can sing a rainbow, sing a rainbow too. A lighter moment for a few impoverished MPs.
Apparently, it was Isaac Newton who gave us the familiar 7 colours: Red, Orange, Yellow, Green, Blue, Indigo, and Violet. The story goes that he decided there should be 7 colours to match the seven planets then known and decided Indigo should fill the gap. Newton was a bit of a mystic sometimes.
The Impressionist's modern, if jaded, eye registers only siz colours: Red, Orange, Yellow, Green, Cyan, and Violet. Maybe the planet Cyan was unknown in Newton's day.
Some people claim that the whole idea of the «colours of the rainbow» is another story to tell little children as it's thought to be easier than trying to explain a continuous spectrum. Like many other aspects of education, the idea has been grossly over-simplified to make it easy to teach, not because it has any utility. Knowing the name of something tells you almost nothing about it.
The rainbow has a continuous range of wavelengths - so a rainbow contains every possible hue. And of course the human eye can distinguish far fewer than the 16 million or so hues (2 to the power 24) claimed by some purveyors of graphics and video technology. Assigning a name to each of these would be as pointless as it would be time-consuming. I expect there's a government department looking into it.
For everything you could ever want to know about colour, look at
Charles Poynton's Color FAQ page. Not recommended for politicians.