Typically on most car stereos the red is 12 v (+) switched, black or green is 12 v (-) and yellow (sometimes blue) is 12 v (+) continuos for memory presets. Not sure why you would need the distinction if "WW" is some kind of trailer with no ignition switch. As suggested, look up your stereo model on Google and see if you can download a PDF manual if you don't have one.
If it works on a car battery, check the ground wire to be sure it is still connected. It shouldn't be too hard to string new wires from fuse panel to the stereo if the originals are pinched or cut by the slide.
Bob & Donna
'98 Gulf Stream Sun Voyager DP being pushed by a '00 Beetle TDI