If you click the "Start" button, you will successively see a number of words that are names of colors. Each word is written with letters in a certain color. Try to name as fast as possible (out loud) the color of the letters in which the shown word is written. This means that you should not read the words themselves! After each word, you will see a colored dot that shows the color that you should have said.

You probably noticed that it is rather tough to say the names of the colors very fast, since your brain is also reading the text, which is almost unavoidable...