I'm not sure of the correct terminology here as Microsoft keeps changing it and well, I tend to think in terms used by Apple in GS/OS (the Apple IIGS operating system, although very similar to the Mac's System 6.0.8) back on my first computer.
On the scrollbar is a shaded region that shows roughly where you are in the document, and clicking above or below that can make you scroll by a screenfull at time. Apple called it the "Scroll box" back with GS/OS in the late '80s. I've been using that term since.
However, distinguishing the shaded part from the non-shaded (it varies with the amount of vertical scrolling available) part is difficult in Windows 10. The contrast just isn't enough as the shades are too similar.
On earlier versions of Windows this could be adjusted, but those same registry entries don't work.
I know it can be changed because of what happens if you choose "high contrast display", but those are ugly.
Has anybody found a way to actually adjust the contrast between the two colors used on the scrollbar and the scrollbox that works in win10? The built-in solution works just fine in Windows 95 through Windows 7.
Here's a pic to help describe what I'm talking about.