var defaultStyle = new GC.Spread.Sheets.Style();
defaultStyle.backColor = "LemonChiffon";
defaultStyle.foreColor = "Red";
defaultStyle.borderLeft = new GC.Spread.Sheets.LineBorder("Green");
defaultStyle.borderTop = new GC.Spread.Sheets.LineBorder("Green");
defaultStyle.borderRight = new GC.Spread.Sheets.LineBorder("Green");
defaultStyle.borderBottom = new GC.Spread.Sheets.LineBorder("Green");
activeSheet.setDefaultStyle(defaultStyle, GC.Spread.Sheets.SheetArea.viewport);
var cstyle = activeSheet.getDefaultStyle(GC.Spread.Sheets.SheetArea.viewport);
alert(cstyle.backColor);