Nissan's don't have a factory ground wire (the factory radio recieves it's ground through the antenna but that ground isn't good enough for aftermarket radios). You need to ground the black wire to the actual chassis of the car. You might be able to find a screw you can connect it to, or you may need to screw it into the chassis yourself. The cigaratte lighter is accesible, you could also tap the ground wire of that.
SOunds like a mess.those color codes are a pain.Go to the store walmart,etc. Get a light tester from the auto department.Use the tip on a positive wire or cigarette lighter and use the clip to find the ground.Be careful cause sometimes the speakers ground also.But this way is safest and best.Also to find positives as well