Whether or not a discoloring motion has been performed by a player character is determined, and a discoloration portion set for the determined discoloring motion is discolored. A discolored mark texture of which the discolored mark pattern is denser and of a thicker color is mapped as a current discoloration value set to the discoloration portion becomes larger. The current discoloration value is added and updated by a discoloration unit set based on the stadium in which the game is performed and the game day weather each time the discoloring motion is performed.