It may be necessary to degauss a monitor to improve the color around the edges of the screen. This kind of discoloration is caused by magnetic interference around the monitor.
Power off and then power back on your monitor. Most monitors will degauss automatically when turned on so try this first.
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.
Locate the degauss button on the front of the monitor and push it. In the rare case the monitor does not automatically degauss, you can try manually doing so.
Tip: The degauss button will most likely be accompanied by a picture similar to a horseshoe.
Press the brightness and contrast buttons at the same time.
Some monitors don't have a dedicated degauss button but instead require the simultaneous pressing of multiple buttons.
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.
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.