Your TV is the problem, not the console or cables. Looks like it doesn't support NTSC colour.
Since the TV can't interpret the NTSC colour encoding you're left with just the luma and the image displays in clean black and white.
The same TV has no problem playing my Japanese Dreamcast games or Dreamcast games when using the 60hz option when prompted with some games. So thought it would be fine here, but hey guess not
Using the same cable and putting it into my HDTV I get a colour picture albeit a bit on the dark side.
Searched and found that others were suggesting a modded cable?