Fair play is affected by the way you play. It will eventually go lower if you tend to time-out and forfeit during your battles. There are percentage which are determined by those battles. Your fair play rating will vary thru the colors and the smily faces (Yellow - smiling face "100%", green - semi smiling face "99-96%", orange - almost frowning face and red - the frowning face). The percentage represents the number of expired battles that you had.