One of the suggestions on the google search that I don't think has been tried here yet.
"Some TV's will work straight on your AV channel, others need the settings changed for that channel via your remote control to except S-VHS etc."
"I had a similar problem once and it was resolved by going into the settings of my AV channel via the remote control and configuring it for s video."
Maybe play about with the TV that give you a Black and White image to see if you can break it or fix it.
