These sets have a history of bad picture tubes, the blue is most common, there is a way to without replacement of any parts to attempt to correct this.
you have to remove the entire grill on the front below the screen; it is usually held in either by two screws at the front (under little plastic caps) and or screws on the back on either side.
The grill will pull out and is engaged with large plastic tabs at the top; with it out since the front keyboard is mounted into it you lift and tilt it to the left. Remove the inspection plate behind it: look for the screen/focus block (see attached photo) and note the six controls: three are screen and three are focus----do not touch the focus ones.
They are usually marked (may be hard to see: r,g,blue) You want to locate the BLUE SCREEN CONTROL and with the set on on a unused video input turn the screen control SLOWLY (usually to the left) until you see no blue in the background; if you do it correctly all you should see is the Video 1 etc.
The idea here is to lower the blue screen setting just slightly-if it works you may only be buying some time as these sets are prone to problems like this.
I have done this several times and many see a few more years of use before they have to be replaced.
Let me know before you attempt this if any questions.