3.5mm cord phone to speaker

[stevielocs42109]

I'm want to connect a 3.5 mm cord from a car speaker to my phone making a portable speaker for my phone. The cord has 3 wires, colors are red, green and normal wire color gold. Which color wires go to the + and - on the car speaker? Thank you.

 

[Alabalcho]

@Stevie - post pictures of whatever you got, especially that cord with "red, green and gold".

Is that "car speaker" powered, or is just a bare speaker with flat (bare) wire?