Buying a pinball off eBay these days is like chook lotto.

As Rob said, build up the area around the hole before fitting a cliffy.

The monitor probably needs to be degaussed. These color distortions can be caused when moving the machine or when placing it next to items with a magnetic field. The motor in my Garage door does the same thing with arcade monitors. Could be a simple case of leaving it be as the chassis may degauss the tube over time anyway.

Make sure transformer has the Faraday cage surrounding it and its tapped to ground... lack of the cage will cause colouring in the tube also