The words themselves interfere with your ability to quickly say the correct color of the word. Two different theories have been proposed to explain this phenomenon :

• Selective attention theory : According to this theory, naming the actual color of the words requires much more attention than simply reading the text.
• Speed of processing theory: This theory states that people can read words much faster than they can name colors. The speed at which we read makes it much more difficult to name the color of the word after we’ve read the word.

In psychology, the Stroop effect is the delay in reaction time between automatic and controlled processing of information, in which the names of words interfere with the ability to name the colour of ink used to print the words.