From Tom Scott.
Grey? Blue? Purple? It can look different, depending on the context. Let’s talk about color perception, color temperature, and the history of laundry.
The optical illusion is original, but based on the work of David Novick: https://twitter.com/novickprof/status/1139342022551191553
More on Illuminant D65: https://en.wikipedia.org/wiki/Illuminant_D65 – the references in this article go into the full technical detail