I have a monochrome system with a fixed rear camera and it's just fine. It has provisions in the monitor for a second camera.
What I need to do is get a camera that I can temporarily attach to the front LH corner of the rig, looking along to the rear so that it shows where the front and rear wheels are, relative to the edge of my driveway. Even after trimming off the roof overhang as far as possible, I only have about 6" clearance on the right side, so getting the left side as close to the edge as I can, is critical.
Dave, do you want to sell that wireless camera that's sitting on your garage shelf? Send me a PM.