Thanks for replying ... I'll try to give you a bit more,
It's the same projector, an Optoma Themescene, although mine is the HD72i model.
When it powers up there's a small grinding noise for a second then everything comes on as normal albeit all green, including the menu, welcome screen etc.
It's not the cable as it's connected to a PC via DVI and a PS3 via HDMI and both sources have the same problems ... green in RGB or when I switch it to YCbCr in the menu the colours look, well rough, and as I say they have almost a corona around them.
It's hard to describe but if there was blue logo, it'd have a rough blue-ish ring around it that increases or decreases as I play with the colour, brightness or contrast settings.
I downloaded a colour chart, put it on a memory stick and displayed in via the playstation. The colours all look a bit dull, with the reds appearing almost brown and no amount of tweaking with the settings is helping.