I have a visual impairment that make it really hard for me to distinguish objects where the is little contrast. This new UI trend of one pixel borders is a big annoyance for me. I constantly click the wrong window.

I actually wrote a Windows app to do something like this. It's sitting in my unfinished folder because I ran into too many issues to fix for a hobby project. The rectangle data for Windows apps seems to vary widely. I needed a bunch of different formulas to correct for the rectangles I was getting back from the WinAPI calls.

One of my features was a different border color for each app. I tried various color rules, such as multiple copies of VSCode would each get their own shade of blue, or cycle through colors of the rainbow.