That "1" is usually white.
This has happened before, this time last year. No idea what caused it, but it only went away after going through 3 different new monitors. Today, however, it has returned. I've not installed anything, updated any drivers, nor buggered anything up for days - it's appeared out of the blue. It's like there's a colour filter being applied to text making it appear all janky and hard to read. I've used my phone to picture them in case a screencap doesn't, but it's pretty damn visible in these images. Here's some more:
Last time out I went through windows support (the official one through settings, not the cringe forum), and the guy said it's hardware...but I don't believe that. This is on a different gpu (AMD, now Nv) and different monitor to when it occurred last year. Any ideas?