Your task is to say the colour not read the word:
RED
BLUE
GREEN
PINK
BLACK
RED
YELLOW
PURPLE
GREY
ORANGE
Did you find that tricky? Once reading has become automatic, your brain can’t *not* do it. This gives copywriters a power and responsibility when we’re writing text for posters, headlines and subject lines that people just can’t miss.
More about the ‘Stroop effect’ on Wikipedia