//Note: This code only works with V9 or earlier versions.
var style = new GC.Spread.Sheets.Style();
style.backColor = "lightgreen";
style.foreColor = "red";
activeSheet.setStyle(1,1,style,GC.Spread.Sheets.SheetArea.viewport);

var style2 = new GC.Spread.Sheets.Style();
style2.foreColor = "black";
style2.copyFrom(style);
activeSheet.setStyle(1,3,style2,GC.Spread.Sheets.SheetArea.viewport);