Set everything up to use RGB.
To record Tivo to DVDR, just play the programme on Tivo and record from the SCART input on the DVDR.
One reason you could be getting black+white is you are using the composite signal (not RGB) and are recording an NTSC source to PAL (or vice versa??) or your TV cannot handle NTSC and so loses the colour information. Are you sure the DVDR is recording black+white and it isn't a problem with your TV? (play the DVD in another player & TV like round a friend's house).