Projector loses colour with hdmi source

BenPink
BenPink Member Posts: 1 New User
We have a P1220 DLP Projector which has suddenly stopped working in colour when connected to a hdmi source.  It works in colour using video-in and still works in colour when using a hdmi cable fort sound via the dvd 5.1. But if I change the source to hdmi, it becomes monochrome.  I have tried different hdmi cables and different hdmi sources. I have tried to clean it of dust. Any clues as to why this switch of source causes the loss of colour? Thanks.