I know that the idea of black toilet paper is traumatizing nomis! ;-)
So here it is, using the CSS "!important" trick to override GTK+ CSS
recoloring code.
In order for the icon to be always visible, even on light background, I
am adding a path around the toilet paper shape (which this time will
be properly recolored by GTK+ with the foreground color, hence making
the icon clearly visible).