They say Newton was half mad.
That when he first split light by passing it through the prism, he saw 6 colours not 7.
But he was first and foremost an alchemist, and in an alternate world where he had succeeded to convert base metal to gold, Principia Mathematica would just be a footnote in history. And in alchemy, the number 6 is ugly. There’s an elegance and a symmetry about number 7 that 6 can never match.
So Newton conjured up the colour indigo out of nowhere to add to the 6. We had our Vibgyor.
Nowadays we say how curious it is that there are 7 days in a week and 7 colours in a rainbow but we got the correlation backwards. The number 7 is just a construct which has grown on us leaving 6 behind causing us to link it to whatever we value and whatever that’s useful to us. The drawing of a rainbow is as inaccurate and relevant as that of 9 planets orbiting the sun but it is now indelible in our collective consciousness. Both drawings make purists mad but add that simplicity to a complex existence, a layer of understanding of the broader world which though untrue, isn’t false altogether and we are better off with this half-truth.
Indigo isn’t necessary for the existence of a rainbow. It doesn’t make the tiniest of difference to our eyes which pretend to see it but never do. A rainbow can exist perfectly well without the additional space taken up by indigo and no one would have noticed its absence if Newton didn’t bring it up into existence. I sometimes wonder whether the rainbow itself even notices it’s presence, but it’s sneaked itself in, like it or not.
Some of us aren’t really ambitious.
All we want to be is the indigo in someone else’s rainbow. Quiet, unnoticed. But always there.