Black level

You misunderstand.
This is not about a 1% adjustment. And it's not about getting the two monitors to match. (To my eyes they're perfectly matched already.)

The "vibrance" setting has apparently been 50% since day one. And the screen has been dark gray rather than black.
I can bump the vibrance up or down, a little or a lot ... and the background becomes a nice dark black.
I can then set the vibrance back to the original 50% (or any other setting) ... and the screen stays nice and black (for a while).

The same is true for BOTH monitors.

At this point I'm inclined to cheat:
1. Find a GUI test/controller software tool that will open the Nvidia control panel
2. Have it jog the vibrance control up and down
3. And exit.

I'm sure there's a way.
Application test/automation people know how. But I don't.

Personally I would reset all the Windows and Nvidia display settings back to the defaults (and disable the digital vibrance), and use the monitor's own controls to get them the way you want. That way you don't have Windows or the Nvidia settings being forgotten.

Did that. No luck.

I don't know what is causing a perfectly good black background to change to dark gray. And I don't know when it happens ... but maybe it goes gray after a "wake up"?

By that I mean ... I had Windows power settings as: "When plugged in, turn off [screen] after two hours". Maybe after the screen goes blank/idle, and then I "wake it up", the screen goes gray?

So, I just now changed that setting to "never" turn off the screens. And I jogged the Nvidia vibrance setting, as before, to restore the black background.

Maybe this will prevent the return of the gray background? Time will tell.

After logout and login ... back to gray.

I have the same graphics card and it did the same thing where when you adjusted the digital vibrancy it would change to darker blacks and make for a much prettier picture (The colors were way more natural looking). As of yesterday all of a sudden doing so doesn't change it and it's stuck with the grey look.

Does anyone here know why it would go away and what I can do to make it come back? My best friend updated my drivers yesterday which is when it happened so I don't know what I can do. All I know is the gray's are driving me crazy.