Most US plasma TVs/monitors have S-Video as well as component and composite video inputs.
Unless your source has component output then you will not need it. Only my DVD player has component all the rest are svideo.
The closest thing to SCART is SVideo. But there are problems coverting between them because SCART on makes all of the SVideo lines available one way, you get black and white going the other way.
Check out http://www.videocapturecard.com/svideoscart.html for more info.
I did buy one of the cheapo cables and it does indeed only give B&W.