Thanks to Andante_in_C who told me what it is called!
This is an experiment that used to be at the Science Museum in Bristol (may well still be I guess!)
Words for colours (ie blue, green, red) were written in the colours they represented, and then in completely different colours, and you had to try saying the colours the words were printed in. Surprisingly hard! If your brain is tuned into blue meaning blue, then you actually (assuming your English is good) comprehend the meaning of the word more quickly than the colour it is printed in, and so if you see red printed in blue it takes a lot of concentration to quickly say blue and not red. If that makes sense (and I do hope I got it the right way round!)
As an example: As fast as you can, read out loud the colours that these words are printed in (not the colour that they are)
If you're anything like me (and as far as I remember mine is the "normal" reaction...) then when the words start being in different colours to the meaning of the words, you suddenly start speaking at about half the speed and still make masses of mistakes!
If you squint and blur the words then it's easier to say the colours.
Might be quite different for someone whose native tongue is not English or who doesn't read fluently in English.
blue red green yellow blue red pink purple orange red pink blue red orange purple blue purple purple red green red green pink yellow red purple blue red blue yellow red green purpleyellow red green orange red pink blue red purple blue red purple blue red orange blue red pink green red pink blue blue red green yellow blue red pink purple orange


