Check fuses as you've prolly blown illumination. Don't use the grey wire at all, tape it up. Black is not earth as there is no wire on the other end of the plug so earth it directly to steel behind the deck anywhere as it's currently getting it's earth through the antenna.
Illumination (cars orange wire) will show an earth until you turn the lights on then it will change to 12v.
If your new deck has illumination on it (orange wire) connect it to the orange wire in the car, if not, tape up the cars orange wire and leave it unused.