Many years ago I worked in the golf course turf industry. With a "bent" type of turf verses a Fescue, as the rollers (on the reel mowers) roll across the turf, it lays the blades of the grass down in the direction you are mowing. So if you mow one direction, then the oppisite direction, you achieve your stripes just by the way the light hits the blades of the grass. You can get striping without even trying.
ive been told its a sign of a bad deck.but they make kits for it.