Yeah, I hate those older harnesses that had mis-matched wirring colors...

Good choice on the deck, i'm sure you'll love it!

I noticed you already took the high amperage power wire into consideration. A good point to get the power for the wire is right at the kick-panel fuse box. Just above the fuses is a row of power terminals... run a 12 gauge wire from the yellow harness wire to the fuse box area, terminate the wire with a .25" female disconnect terminal. The terminal closest to the fire wall should be the constant power terminal, but check it with a test light to verify. Also, with the ground wire, be sure to chassis ground it, instead of the car harness. All that power getting to the deck is useless without a proper ground.

Hope the install goes well for you.