When I plug in VGA there is a green mask or Hue, over the whole screen... I tried changing the settings but its not controllable with colour settings

There is some color format mismatch. Look for settings and try to correct it. You may go through the operation manuals of both step by step. Also check whether the frequency of the device is same like both are of 50Hz or 60Hz.

Have a very close look at the blue and see if it's perfectly uniform across the whole screen.
If it is then altering the hue or colour temperature settings in the menu may help.
If it's not then either there are heaps of pixel failures (appearing as small rectangular spots) or degradation of the polarisers (green may be affected more than the others).
If you show the menu, do the white areas appear bluish.
If the lamp is very old then colour changes start to happen.

If the yellow tint is uniformly over the whole screen then try changing the video colour tint, hue, phase and other chroma related settings in the menu.

Most monitors have colour balance settings, these can be accessed by buttons on the monitor, trying looking around and adjusting colour balance, hue and other settings

Try changing your vga/dvi cable,or it could be colour decay.

Tv repairman. the green picture tube has an intermittent short in it. This is an expensive fix.

Your AUTO settings button is stuck in! Try tapping on it a few times. Otherwise you may have to take the frame apart so you can get at the button.

Yes, I'd say your cable is faulty. If it is the type you can disconnect, then change it. If it is moulded to the monitor then you might have a problem. check all of the pins on the connector to make sure they are in tact and not bent.

Problem resolved by swapping the video cable, simple really!

Change posistor in the degausing circuit.