Well the white screen is a good sign; it means the high voltage and other main power supplies are working find. But you mentioned that you tried setting the color and brightness and it didn't help so I guess it might be in the video processing area - a loose connection or cold solder joint. Most technician would disassemble the unit (if you know) then detach and re-attach the connections like the ribbon wires. Combination of electrical tape and used static foam would help to strengthen the hold.
But if you have second thought on these - go find a technician to be safe.