Originally Posted by
joshwex90
Looking at the map, what do the green, red, and yellow lines represent?
They represent the different AirTrain lines.
Yellow is the "inner loop" AirTrain that runs clockwise and only visits the terminals.
Red and Green are the "outer loop" AirTrains that run counter-clockwise around the terminals and then leave the airport to take you to Jamaica (red) or Howard Beach (green).
I'm pretty sure the colors only exist on the map, though. When you get to the train they are referred to by their destinations and NOT by colors.