Hello! i am installing and aftermarket stereo in my Mercedes ml350. i bought a pioneer MVH-1400NEX stereo with a premade wiring harness. when i turn the car on the display turn on and everything seems to work, but i do not know where to hook up my backup camera. is that what the three seperate plugs were that arent part of the wiring harness? there is a yellow, a blue, and a green one.