it's actually not a "left-right" brain conflict
it's actually a demonstration of the level of automation of differant thought processes
we've read things all our lives and because of this it has become an automated process, we can't but help read everything we see, and we do it really fast, recognising a colour and thinking it's name is a slower and unfamiliar process so it is hard to override the automated process with one that is not automated
those who didn't make any mistakes try doing it faster