Are you sure it's not a black and white TV?

Just kidding.

As far as I know, the things which can cause black and white output are as follows:

1) Having the incorrect mode set i.e. NTSC instead of PAL (it may be worth trying different modes)
2) Your TV not supporting SVideo in through SCART. Note that the Scart adapter you have simply makes the SVideo cable "fit" into the Scart socket, but your TV has to actually support one of these adapters (SVideo through Scart). If it doesn't, only the luminance will get through (black and White), this is the problem that my piece of wire fixes.
3) AV modes on the TV. I've seen some TVs where it will have more than one AV mode available for each AV-in. It may be necessary to cycle further through the AV modes manually (usually by pressing AV on the remote) to find the version of the input which supports SVideo in through Scart. Note that if your TV supports SVideo in through Scart, get rid of the piece of wire.
4) If you're using a laptop, I assume you use the function key to cycle between displays modes (i.e. Laptop only, external display only, both). It may be worth trying external display only. On my setup, I have both displays on at once and the desktop spanned onto my TV, I just drag Windows Media Player onto it before clicking the full screen button.

Other than that, I don't really have any more ideas, let us know how you get on.