C# changing backcolor on a cell in a datagridview

I am trying to change the color of a cell in a DataGridView based on the value of the column.  I have tried the following attempts:
 string value = this.dgvMainBottomRow1["colCostedBy", 0].Value.ToString();
 switch (value)
 {
   case "No Ticket Assigned":
     this.dgvMainBottomRow1["colCostedBy", 0].Style.BackColor = Color.Red;
   break;
 default:
   this.dgvMainBottomRow1["colCostedBy", 0].Style.BackColor = Color.White;
    break;
}
  I also tried:
 private void dgvMainBottomRow1_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
 {
  // Check if this is the right column.
  if (e.ColumnIndex == 0)
  {  
    string value = e.Value.ToString();
    switch (value)
    {
      case "No Ticket Assigned":
         e.CellStyle.BackColor = Color.Red;
         break;
        default:
         e.CellStyle.BackColor = Color.White;
         break;
   }
}
When I step thru the code, it is setting the back color properly, but when I view the form, it is still not changed.

Is there a grid setting that needs to be changed?