The Color Signal on this Model Series travels across three boards before being sent to the CRTs. The 3DYC Board, Signal Board and the Terminal Board. Most likely, the 3DYC Board or the Signal Board is causing the problem. I have had intermittent solder connections on the 3DYC Board to cause no color problems. This Board plugs in and is located on the left front of the Signal Board as you look from the rear of the chassis. If you feel you are not up to the task to work on the set, call a Mitsubishi professional. To find one, call Mitsubishi at 1800-332-2119.
I hope this helps,