I have worked in colour pretty much all my life. In 1980 I started learning at the University of Leeds where I was enrolled on BSc Colour Chemistry. That was 44 years ago!

Since 1980 I have been learning, working, researching and teaching colour for almost all of those years. I have learned a lot and I am sure I still have a lot to learn. For example, only a few weeks ago learned that the colour name magenta is named after an actual town in North Italy. I discovered this when doing some research about colour names for the following video.

And I recently I have been learning so many new things from a book called The History of Colour by Neil Parkinson. I can’t tell you how much I am enjoying reading it. But more about that later.

I often say to people that the most important thing about colour that I ever learned is called the principle of univariance. I read about it in Brian Wandell’s book Foundations of Vision in the 1990s. It was discovered by someone called William Rushton in the 1960s. It is about how the human cones operate and it is so fundamental to explaining how colour vision works. It explains how we can discriminate between different wavelengths of light despite only have three types of light-sensitive cells that each have broad-band spectral sensitivity.

It explains why we have metamerism – which is where, for example, two spectrally dissimilar objects can look the same colour when viewed under one light source but then be a mismatch when viewed under a different light source.

It explains why additive mixing occurs. Why we can additively mix red and green light to get yellow. And it even explains subtractive colour mixing if you think deeply about it.

So the video How does colour vision work?, is really about how cones work and the principles of univariance.