DVD player - Picture goes from color to black and white

The TV and VCR give color picture when used. The DVD player will sometimes start up in black and white and stay in black and white. Other times it will start out in color and after anywhere from a minute to 30 minutes, typically 1 to 5 minutes , screen will change to black and white. I pulled the DVD unit and took the metal covers off and checked visually for any identifiable problem. On the flat ribbon cable that goes from the left side of the DVD player and connects to the PC board that the VCR is mounted on, I saw a 1/4" long section of the ribbon where the plastic coating had been wore off (possibly from a spinning assembly line tool that grazed the ribbon cable), and the copper wire could be seen. After reassembly, the DVD player worked as it did above. I tried moving the ribbon cable while the DVD was playing in black and white but there was no change in the picture so I don't know if the problem is within the ribbon cable or elsewhere in the DVD player and I am not shure where to go next. Thanks