You've probably taken action already, but I don't think tweaking an aux output of the switcher is the best way to make the plasma look good on camera.
I would set you cameras up so they match.
Then I would frame the shot that will include the plasma, and feed the plasma bars. Make sure if there are going to be people on the set in the real shot that you have stand-ins.
I would then tweak the controls on the plasma until the bars feeding it looked right on the output of the camera shooting the plasma. You may need to adjust the lighting on the talent to balance the scene.
ps I do not think the panasonic switcher has image tweaks on the aux outs, but I'm not sure. If you find the controls on the monitor are inadequate, I would find a separate color corrector or tbc to improve your ability to adjust the look of the plasma on set.
we have had a lot of issues getting plasma screens to look good - often the recorded image is way too blue - we also need to set the shutter speed/clear scan setting on the cameras to match the refresh rate of the screens. I think you can use color correcting filters on the screen itself, akin to putting sheets of ND on a window. Definitely need to test this before the shoot.