green screen

For the past couple of months my phone has done this thing where the screen will randomly freeze while in use, and turn the screen completely green and it will stay like that for days on end until it turns back to normal. The only thing thats recently changed in the newer months is that the screen has always got a small section in the top left of the screen which doesn't turn back to the original screen it stays green, but as of now the phone screen is green and would be the longest time its been green. Are their any suggestions or fixes?, or do i need to get the screen replaced?. Thanks