PlotArea dataLabel colour chage

Hello Experts.

How to change color of plotarea datalabel. Which property should I use in addtion.?

  oVizFrame.setVizProperties({

            plotArea: {

               dataLabel: {

                    visible: true,

                    formatString: "#,##0",

                    colorPalette: ["#FFFFFF"]

                            }

}

It seems colorPalette does not work here.

Thanks,

Ashik