[GNC] Change GnuCash scrollbar color in CSS?

[Glenn Fowler]

Hi,

Does anyone know how to change the scrollbar and scrollbar button color in
gtk-3.0.css?

I have tried:

scrollbar slider {
    color: blue;
}

and...

scrollbar button {
    color: blue;
}

Both have no effect. I didn't find anything in the mailing list archives
and the above I got from generic GTK CSS.