A handy addon for customized scrollbars with tons of options
After installation, you'll see a link to Styled Scroll Bar in the sidebar of the concrete5 backend. The backend form is tidy, clearly arranged and each option for customizing the scrollbar is well explained.
It is even possible to define your own DOM selectors to trigger nicescroll. This means, that not only the scrollbar of the browser window, but scrollbars of any scrollable element (e.g. with defined height and overflow: auto or overflow: scroll) can be customized, optically and functionally.
The author's support is incredibly fast and helpful!