Question: Why did you pick yellow and blue hats for the demos. And what is the probability of picking these two colours out of all the known colours?

Dominique Sleet answered on 3 Jan 2020:

The probability of us choosing those two colours is actually quite a complicated question. Firstly how many different colours are there? Some calculations state that humans are able to see 10 million different colours so in which case picking those 2 colours out of 10 million is very unlikely indeed! However whilst our brains might be able to distinguish that many colours, it would be very silly for us to choose a shade of blue and then a very similar but technically different shade of blue. We wanted to pick two different contrasting colours that were easy to see among our audience.

We could pick two different colours at opposite ends of the colour wheels to ensure maximum contrast. Colour wheels often show 12 different colours so in which case you could say the probability of picking blue and yellow from these 12 colours was 1 in 66. However we also wanted to avoid combinations of colours that were difficult for people with colour blindness so that narrowed our colour options. Add in the limitations of what colours were available to bulk order at late notice and blue and yellow ended up being pretty much being our only option!