Fix Sticky Scroll Color Inconsistency in Visual Studio 17.12.3

[Guuugao]

First off, thank you for creating such an awesome theme! I've been using it and absolutely love it. However, I recently noticed a small issue after updating to Visual Studio 17.12.3. The sticky scroll (enabled under Tools > Options > Text Editor > General > Sticky Scroll) seems to have colors that don’t quite match the rest of the theme, and it looks a bit out of place.