N64 Picture Quality Help?

I'll try to explain it in as much detail as possible. So, basically the picture quality on my N64 is not as good as it should be. Text becomes almost unreadable sometimes, there is not as much colour as there should be and sometimes it even shows some colours to bright. I'm almost 80% sure that it's not the console, because the problem is with BOTH of my N64's, but I'm not sure if it's the cable, because it works with the SNES ok. Hope I'm not being to vague.