Identify Reverse light wire color

I am a newbie here. When it comes to DIY car stuff I am a beginner. Got a Vantop backup camera kit. I need to connect a wire to the reverse light wire to serve as a trigger when the car is put on reverse. When I open the cover in the back of the hatch door, I don’t know which wire to connect to. So I opened the rear light unit and saw there is a red wire with blue stripe (+) and a white wire with black stripe (ground). But these wires don’t show up in the hatch door. The camera is being mounted above the license plate. Is there any other wire I can use? or How do I connect to that positive wire of the reverse light?