This needs to go to the monitor section (You can also post over @ KLOV's Monitor Section, as they have some real dedicated monitor guys.)
The white stuff is silicone, it's there to stop vibration noise, as some parts switch at audible frequencies, and it's annoying.
If you can turn the screen blue with the bias pot, then you need to follow your JAMMA harness back and check for a break in the blue line. If nothing is wrong there, then you're going to be looking at a chassis problem. Need more pics to be able to tell what sort of monitor you've got there.