Does artificial turf have a nap? Here is a PHOTO that shows how nap makes fabric appear two different shades due to how the nap catches light. You can feel a nap by brushing it one way with your hand and then the other way. Brushing with a nap will feel smooth, but your fingers will feel resistance brushing against a nap.

If you can feel a nap, then flipping the section 180º might resolve the issue. However, if the section was turned 90º from the others to begin with this won't do anything. The fix will be to add something that draws the eye away from the line.