Bolero wiring

Hi can anyone tell me which is the negative wire that is connected into the back of the radio which is contained in the plastic plug.   After fitting the Bolero into the car in place of the Stream head unit this has fought me every step of the way,  Antenna plug breaking off, electrical instruments going crazy, Broken trim etc....I have decided to put a switch on the negative wire to isolate the radio from the power supply so as not to cause battery drain...I know fitting an upgraded gateway is what it needs but ive had that much hassle fitting this thing its probably not going to go smoothly to plan 😁..Plus i know i will have to enter the security code every time the radio is powered up again....Thanks.