flip down monitor wiring

with my last ? answered i have come up with another one. i got a great deal on a flip down monitor, it came with all wires & remote.hooking up the monitor is not a problem, its the dome/reading lights. it has 3 wires a red(constant) a black (neg),and a yellow (to turn on dome lights). i tested on my bench the yellow is a ground? where should i wire this to in a 90 suburban?

next i have 3 faint black scrolling lines in my 7.2 in dash monitor and my 5.6 headrest monitors,if the car is running or not. i pulled my dvd player, an hooked it up to my house t.v. and there are no lines in the pict, so i pulled my dash monitor and hooked it to my house vcr,and there were no lines.i did the hole wireing on oppisite side thing.should i seperate the factory wire loom that came with the monitors,to get the power away from the video wires? thanks for the time.