I have a DMR-EH50 and I have discovered that the scart plugs can be a pain. You must have the lock-in type, ones with lugs, otherwise the connection can throw up any number of faults and it sounds as though one of more of the primary colours is playing up in some way.
Scart plugs seem to be all cheapies in a lot of outlets so a reputable TV/Video/DVD shop is the first stop IMHO.
Good luck.