I say ‘plum’, you say ‘purple’.

The science of colour vision, and how our eyes and brains perceive colour, is fascinating.

Reblogged from MindShift, here’s a link to the top ten most popular educational videos on YouTube in 2013. Look at how many of them are about science! I haven’t watched them all, but I especially like number 4: Is Your Red The Same as My Red? from the Vsauce channel.

I worked with lasers in Birmingham University Chemistry Department, and from this and from my general scientific background I knew that we could take a single wavelength of visible light and say that it had a specific colour. But how do our eyes detect that colour? Inside our eyes, we humans don’t have specific detectors for each wavelength. Instead we have only three types of receptors (cones) each of which responds to a broad range of wavelengths, and two of which have ranges that overlap significantly. The combination of signals from each of these gives us a pattern which we then say is ‘red’ or ‘purple’ or ‘yellowy-orange’.

How do I know that your red is the same as my red? I don’t. Humans have quite wide variation in how their cones respond to the same wavelengths of light, and some women even have an extra sensor which gives them what is known as tetrachromatic vision (like some birds).

Our descriptions of colour seem to be limited by our language and our experiences, as discussed further in this post on Psych 256 (with references, which I haven’t provided here) and on a 2011 post on the blog EagerEyes.

There’s some very in-depth explanation of colour vision on the relevant Wikipedia page, and if you really want to study it further I highly recommend the Open University course SD329: Signals and Perception. The course materials are all available online. It is a Level 3 course, at an equivalent level to the final year of an undergraduate degree, and the OU has conveniently prepared a guide called ‘Are you ready for SD329?‘ (pdf file) for people to check if they have the appropriate background and experience.

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