So I have a redline on one of my monitors. I looked at a few posts a bunch say clean the ribbon, degauss (which my monitor doesnt have the option for). I was wondering if there could be another cause. Something to note is that when I make the screen all white, yellow (or red obviously) the line goes away.
If this is an LCD (flat) monitor degauss will not be an option. Typically this means the screen controller is having trouble or the LCD panel itself is going bad.
In the past I have had some success resolving single stuck pixels in LCD monitors by playing a video of quickly-flashing bright colors, but it has been some time since I have tried this, and that was usually for single pixels that were stuck.
If the line goes away when the screen is a solid color this seems to me to indicate a problem with the screens controller rather than the LCD panel itself having a problem. Sadly this would mean issue is unrepairable.
As always, though, try the simple things first: Remove your video drivers and reinstall them. Try connecting the screen to a different computer and see if the issue persists. Look at the screen when the computer is off (pressing the On Screen buttons will usually light the screen up briefly.