DO not know if this is the solution for you. But a while back I was hooking up a roku using composite cables to a tv which did not have a working network port. I did not see anything labeled composite on my TV so just trying matching color and then even do any of the colored ports. Finally got a picture but it was black and white.
If you are using the 3 colored rca connections (the composite wires) , make sure you have them in the correct jacks and make sure you have chosen composite for the source (on my tv instead of saying composite it said video). When I got them plugged in and chose video as the source, I had color.