"In psychology, the stroop effect is a demonstration of interference in the reaction time of a task. When the name of a color (e.g., "blue", "green", or "red") is printed in a color not denoted by the name (e.g., the word "red" printed in blue ink instead of red ink), naming the color of the word takes longer and is more prone to errors than when the color of the ink matches the name of the color." (Wikipedia 2015)
In this game, you will see a big label, and all you need to do is to name the color of the text. Ignore the meaning of the word in the label, or the colors of the answer choices. Just match the color of the text in the big label with the word beneath it. Easy, right? Try it yourself, and you may find that its not that easy at all!