I had a number of problems getting some video files to play in full colour and after raising a question (http://www.experts-exchange.com/Apple/Software/Q_23484778.html
) I eventually solved it by turning of DirectD in Quicktime.
I haven't played DVDs for a while, last time I played them they were fine (full colour) but playing them now they look the same as the videos did (black and white with a hint of blue, but no other colours).
Alas system restore wasn't turned on on the machine (it is now) so I can't go back to see if recent codecs etc have caused this.
I had a number of codec packs, but I have uninstalled them all and now just have the Vista Codec Pack (4.7) installed but nothing else. Uninstalling all my codecs and reinstalling just Vista Codec Pack didn't change the black & white DVD playback problem.
Any suggestions about how to fix this?