Changing color/style on a scrollbar in a GtkScrolledWindow

I'm having trouble altering the color on a vertical scrollbar in a GtkScrolledWindow. This is what I've been doing: $ScrolledWin = &new GtkScrolledWindow(null, null); $ScrolledWinScrollbar = $ScrolledWin->get_vadjustment(); $ScrolledWinScrollbarStyle = $ScrolledWinScrollbar->style; $copyScrolledWinScrollbarStyle = $ScrolledWinScrollbarStyle->copy; $copyScrolledWinScrollbarStyle->bg[GTK_STATE_NORMAL] = $newColor; //$newColor applied to other objects works OK $ScrolledWinScrollbar->set_style($copyScrolledWinScrollbarStyle); The last line throws an error: call to undefined function set_style()... But perhaps my approach here is more off-base than I'm imagining. Can someone point me in the right direction? thanks very much, dave