blue and green are analog signal of screen touch. The two pots are the representation of the screen.
Who it works :
basicly the screen work like 2 voltage divider. To mesure the touch position you have to apply a voltage to one screen layer and mesure the voltage on one wire of the other layer. then you do the same thing but with voltage on the second layer and mesure on the first.
by doing this many times per second you can track a press, a release and a drag. some screen/controller can even mesure the pressure (commonly z axis).
