Windows 8.1 scroll bars: customisable?
This is possible, at least for desktop mode on Windows 8. You'll need to add support for custom themes though, and there's a nice tutorial at http://www.howtogeek.com/168270/how-to-install-custom-themes-and-visual-styles-in-windows/ for doing that. Once you enable support, you can find a theme that offers the slider bar with a different color from the rail. Really, from after you enable custom themes support, the sky's the limit.