Joystick wiring help.

[twinforced]

Hello first of all. I'm just starting to get into the wiring of the electronics of my project and now stumped....

I have a joystick.
http://www.pennyandgiles.com/docGallery/103.PDF

I would like to use to control a pair of motors, by using this speed controller.
http://www.ampflow.com/motor_controller.htm

But I'm not sure as how to wire it to the controller. The joystick has 5 wires.

Red... positive voltage supply
Black. zero voltage supply
Blue. channel 1
Yellow. channel 2
Green....................... Center Tap ???

Now on the spec sheet for the speed controller I think I have all but the Green wife in the right place, this is why I need help, please look the specs over and let me know if I'm on the right track or just LOST.

Red........#14
Black......#13
Blue.......#10
Yellow....#11
Green..... I dont have a clue.

Thanks .