Color problem MAG Innovision 14" monitor

I've had this monitor since 2003 with no problems. Last week while the kids were on the computer using the Fisher Price Digital Art Studio, the "hue" of the entire screen turned a shade of yellow. The color went back to "normal" after a few minutes, but then returned to yellow. I unplugged the USB that connects to the art studio tablet but the appearance remained yellow. I've also shut down the pc, shut down the modem, and un-installed the art studio software off the computer. I also tried adjusting the color on the monitor itself, but can't get the color back to normal. The color has remained a shade of yellow for almost a week and then a few minutes ago while I was on the computer, the color changed to a "hue" of green. Any suggestions>