I am adding a factory sub box and aftermarket mono amplifier to my X5. I would like to run the 8ohm subs in parallel to bring them down to 4ohm (I believe)

The factory subs have two sets of wires coming from each. Can someone tell me why?
I am guessing that I need to connect all the green wires and all the green and black striped wires so I end up with just two wire leads?

Any advises is appreciated, thanks!