Data Controls :: Change Color Of GridLines In GridView?

how to change the color of gridlines?

I tried 2 codes but its not working:-

protected void MyGrid_RowDataBound(object sender, GridViewRowEventArgs e)
{
foreach (TableCell tc in e.Row.Cells)
{
tc.Attributes["style"] = "border-color: #c3cecc";
}
}

and

protected void Page_Load(object sender, EventArgs e)
{
this.MyGrid.Attributes.Add("bordercolor", "c3cecc");
}