From what you are describing, I would most likely suggest that you have broken a wire in the harness of the monitor.
9 times out of ten,, it is just in front on the plug that attaches to you video card. The wire will be bent at an angle that exceeds or is equal to 90 degrees.
The cause: Pushing your computer too close to the wall,, or setting your computer too far back in the desk.
Minor movement in the cable will cause the small wires to experience fatigue and break,, you will lose a color , all color , or all picture. The fact that you are seeing green leads me to think one wire.
Resolution: NEW MONITOR.
the harness is hard wired into the control panel inside the monitor, so,,if you have an old monitor and are really good at soldering you have yourself a little job,, if not >>> $$$$$
cheers