//Note: This code only works with V9 or earlier versions.

<input type="button" id="button1" value="button1"/>

var style = new GC.Spread.Sheets.Style();
style.backColor = "lightgreen";
activeSheet.setStyle(1,1,style,GC.Spread.Sheets.SheetArea.viewport);

$("#button1").click(function () {
style.clear();
activeSheet.suspendPaint();
activeSheet.resumePaint();
    });