formStyleFormat = new FStyleFormat;
formStyleFormat.scrollTrack = "0x123456";
formStyleFormat.highlight = "0x000000";
formStyleFormat.highlight3D = "0x000000";
formStyleFormat.arrow = "0xffffff";
formStyleFormat.face = "0x003366";
formStyleFormat.background = "0x123456";
formStyleFormat.shadow = "0x000000";
formStyleFormat.darkshadow = "0x000000";
formStyleFormat.addListener(myPane); //instance name
formStyleFormat.applyChanges();
That's an example on how to change a scrollpane's colours.
Put this script on the timeline on which you have your scrollpane (most probably the main timeline, I suppose), give your scrollpane the instance name mypane (or change the name in the code) and it should work out.
regards