It appears that you have lost the green colour Boo.
Have you got a menu on your monitor for adjusting the individual colour settings for your monitor?
If so check that.
Also check that the connection to the PC is secure.
Failing this it could be similar to a problem I had a few months ago,which turned out to be a "dry joint",I lost my red colour. I found that if I thumped the monitor sharply it came back ok for a short while,not very technical but it would point you in the right direction maybe