My computer monitor's background has gone yellow.

[Nictuku]

1. If the same thing is happening on multiple monitors...

If the same thing is happening on multiple monitors, the problem is most likely with the Video Card.

You /might/ be able to fix it by re-seating it (take it out, then put it back in)

Here are some steps you should follow if you are going to try this (providing you are able to open up your PC case)

First, very important, shut down the computer and unplug it from the power source.

Open up the computer box.

Find the 'card' that the monitor gets plugged into. See if you can take it out and then put it back in (screws may be involved)

You can google "how to replace a video card' and probably find a YouTube instructions, search for your specific model of PC for best results.

Good luck!