I'm getting ready to install a plug and play satellite radio in my car and i want to splice into the wires going to the cigarette lighter behind the dash (and add another cig. lighter accessory). That way i can plug in my power adapter and hide all of that behind the dash. I opened it up last weekend and saw that the two wires going to the cig. lighter were colored (one black, with a gray line on it...and one green with a red line on it).

I assumed the green one with the red line would be the hot one (+). But, i didn't want to splice it until i was sure.

Does anyone with experience in car audio (esp. with Infiniti cars) know which is which?

Check it with a cheap test light.