ha ha ... def computer. I recently had second Cataract done, and for a time was extremely sensitive to light.
So again attempted to set up the night light 'feature ?" on my PC.
Initially I tried set hours , but that failed. So then I tried Sunrise Sunset setting, which would have been perfect if i lived on Tatooine !.
I now just use the Action Centre . Turn NightLight OFF , which turns it ON

And if I'm lucky both monitors are affected.