How To Degauss the Monitor (some tips for your reference)
1.Most monitors will degauss automatically when turned on so as a first option, power off and then on your monitor. If the discoloration does not improve, continue to the next step.
Note: Degaussing makes a twang sound and is often followed by a short click sound. If you don't hear these sounds, the monitor probably does not automatically degauss when powered on.
2.In the rare case the monitor does not automatically degauss, locate the degauss button on the front of the monitor. The button will most likely be accompanied by a picture similar to a horseshoe.
Some monitors do not have a single button but instead require the simultaneous pressing of multiple buttons, such as the brightness and contrast buttons.
3.Often times the degauss option will be buried in the on-screen menu options. Scroll through these options to locate the degauss option or consult the monitor's manual for more information.
Degaussing is rarely necessary. However, if performing the steps outlined above has not been useful, then probably your monitor is of an older model that might just need to be replaced.
Tips:
1.To prevent the magnetic field disturbances that cause the discoloration on the monitor, check around the monitor for sources of magnetism. This might include unshielded speakers, power sources, and of course magnets.
2.Monitors without a CRT, such as LCD monitors, do not require degaussing.