Your task is to simply name out loud the color of the "ink".  Start by naming all the colors in the first column (the neutral condition).  For example, you should say Red, Blue, Green, etc.   Then name the second column (the compatible condition).  Finally, name the ink color in the third column (the incompatible condition).  Does one condition lead to more difficulty that the others?
 
 
 

You probably noticed that the third column (the incompatible condition) was the most difficult.  The irrelevant color word interfered with naming the ink color -- hence the name Stroop interference.  Stroop interference tends to be greater for patients who have difficulty inhibiting irrelevant information.  Also, as you might suspect Stroop interference is minimal in children who cannot read and increases in magnitude as reading skills become more automated.  Well over 500 studies have been published on this effect (for a comprehensive review, see Colin MacLeod's (1989) article (MacLeod, C. E., (1989).  Half a centuary of reserch on the Stroop effect:  a critical review.  Psychological Bulletin, 109, 163-203.