There is no standard way monitors are wired. Color convention (not all cabs are wired with the colors this way): Red for Red video, Green for Green, Blue for Blue, White for Sync, Black for ground, and two larger black wires for power. It's highly recommended you look for a manual for your specific monitor. You should be able to find the manufacturer and model on the large circuit board.
The easiest way to hook up your X-Box is to get a RGB SCART cable and open it up to get the signals you need. If you're in Europe this is no problem, but if you're in the US, you're probably going to have to import one from a place such as
http://www.lik-sang.com . You could use a component or any other X-Box cable, but it requires alot more work. More information is available at
http://www.gamesx.com