Hi, Found the answer to the background myself: 'trellis.par.get' and 'trellis.par.set' background<-trellis.par.get("background") background$col<-"white" trellis.par.set("background", background) Willem -- Dr R.W. Vervoort McCaughey Senior Lecturer Hydrology and Catchment Management Faculty of Agriculture, Food and Natural Resources Rm 503, Watt Bldg. http://www.agric.usyd.edu.au/mccaughey Postal: Bldg A03 The University of Sydney, NSW, 2006 phone: +61 (2) 9351 8744 fax: +61 (2) 9351 5108 e-mail: w.vervoort at acss.usyd.edu.au