I cant remember the color of the wires but I know they are there because I installed rear speakers in my hatch and the wires were already there. Pop off the rear panel inserts and look around for the wires.. they should be there possibly attached to the harness. Otherwise you could just run a new set off a headunit once you install one.
You can cut holes in the rear panels and make a custom mounting bracket to attach the speakers within the panel, then either use a grille that come with the speaker or make your own. I chose to just mount mine without grilles because no one sits in the back of my car anyway. Still look clean to me.