Replacement Fog Lights

[df_CrewCab]

I am adding aftermarket fog lights and want to wire them with the wires from the stock fog lights that I have. I don't really care for the integrated fog lights. My question is does anyone know which color wire is pos. and which is neg. on the fog light wires? I see a black wire and a purple wire going into the plug.

[top_sgt]

purple should be the positive, black neg.