Why do football pitches have stripes?
What creates the light and dark stripes on a football pitch, why it is not paint, whether the patterns serve any purpose, and how groundskeepers make them.
Not paint, but light
The striped pattern you see on a well-kept football pitch is not created with paint or by using different types of grass. It is simply an effect of light. The grass in one stripe has been bent so the blades lean one way, and in the next stripe they lean the other way. Blades leaning away from you reflect more light and look pale; blades leaning toward you look darker. The result is those familiar alternating bands of light and dark green.
Made by the mower
Groundskeepers create the stripes with the mower. As the machine rolls over the grass it flattens the blades in the direction it is travelling, and a roller often helps press them down. By mowing up and down the pitch in opposite directions, the groundskeeper leaves neighbouring strips of grass leaning opposite ways. More elaborate patterns, such as checkerboards, are made by mowing across the pitch a second time at an angle.
Mostly for looks
The primary reason for the stripes is simply appearance. A crisply striped pitch looks immaculate and professional, and clubs take pride in the presentation of their surface. The patterns have no effect on how the ball rolls, since the grass is cut to the same height throughout; only the direction of the blades differs. It is a visual flourish rather than anything that changes the play itself.
A small practical bonus
There is a minor practical side effect. The neat, parallel lines can help players, officials and spectators judge distances and positions on the pitch, giving the eye a set of reference lines running the length of the field. Some believe this makes it marginally easier to spot whether a player is level with defenders. Even so, the stripes remain, first and foremost, a matter of a groundskeeper's craft and pride.