Handle the PrepareViewStyleInfo event and set the backcolor there if the e.RowIndex and e.ColIndex point to a cell in the row.
private void gridDataBoundGrid1_PrepareViewStyleInfo(object sender, GridPrepareViewStyleInfoEventArgs e)
{
//color row 2
if(e.ColIndex > 0 && e.RowIndex == 2)
{
e.Style.BackColor = Color.Red;
}
}