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