By far the most common cause is the following...
Check that you haven't switched your TV into S-VHS. Some TV AV input sockets are dual purpose, providing Video or S-Video options.
The TV's input must correspond to the DVD output setting or the picture may appear B/W. There will often be an option to select either Video or S-Video in both the TV and the DVD menus.
However, if there is an option to set the connection to RGB, then that is an even better option.
Common video output options are..
RGB
CVBS (Video)
S-Video (SVHS)
Both DVD and TV must match these settings.
Cobweb, January 2006
