Panasonic pz700 tv 50" red screen. Issue - Cell Phones

Hello, I have a Panasonic PZ700 it has started to have a red screen issue, other than that it works perfectly. Their is still blue, yellow, red & green, it's strange & a little bit differcult to explain. Simply way I can explain the tv has Red shading over 60% of the screen! Can anyone explain what the fault is likely to be & cost please!