Hi
In most cases, you'll get B&W picture if your laptop isn't sending the signal in the correct from (PAL/NTSC). Go to your display properties and change the settings of your video-card to fit your TV.
another option is a bad S-VIDEO cable. try checking it with a new cable and see what you get. make sure the cable is short enough (no more then 2 meters if i recall correctly).
You didn't mention your Laptop type but some use different cabaling.
for my DELL i have to buy a "DELL S-VIDEO CABLE" to get colors... check your manual and search for it.