Pics arent necessary....Just play a game in heavy rain on grass...DONT supersim....after halftime, just zoom in to players....You will see it...Its actually more noticable on darker uniforms....might have to do with the lighting...But the DO definitely get dirty....But like TC said...Its subtle.
I have had a game though....Nevada v Colorado St. in heavy rain and my QB,RB and WR had noticable dirt on their pants....As did my C/DE and SS. Was wearing my white pants and the game was at night if that helps some non-believers....