Ok, every TV made in the last 30 years has some sort of “secret" service menu built in. I'm assuming the color balance of the entire screen has drifted, and the problem is not a bad screen. If there's a bad module or screen, making adjustments will not fix the issue.
So the majority of the LG models are ez to get into service mode. Simply press the “menu" or “ok" buttons on the TV and the remote control at the same time. Some TV models have enter/select/set buttons. Whichever buttons work, after a few seconds the TV will pop up a password entry box. Common LG passwords are 0000, 0413,7777. Enter password, press enter/ok/set button. The correct password will open the service menu.
Be careful in the service menu because changing values of the wrong parameters can disable functions and features of the set. What you are looking for is white balance adjustments.