In football, the term "red zone" is used to describe the area between the 20-yard line approaching the end zone. The "green zone," however, is much different-it refers to the space between the line of scrimmage (usually blue) and the first down line (usually yellow).
The green zone came about when the NBC production team decided to digitally shade in the space between the line of scrimmage and first down lines during third downs. It was met with widespread criticism as being wholly unnecessary.
The green zone does not literally physically appear on a football field. Just like the yellow first down marker, line of scrimmage, field goal range line, and other features, it appears on the broadcast only.