Hi,
I've recently had this problem on my 2005 model.
There's a few people over on xdrivers.co.uk with the same thing as well & with their advice I took my head unit out & cleaned the connector plugs & pins ( with contact cleaner ) but this didn't make any difference so next I got access to the tv module in the boot & did the same with these connections.
Colour returned to normal & has been ok for a week now ( fingers crossed )
Hope this helps.
Phil.