DataGridView ColumnHeader does not center all columns

I have a datagridview for which I have set the ColumnsHeaderDefaultCellStyle's Alignment to Middle Center and 3 out of 4 columns are centered, but the text of the second column just stays to the left.

Anyone have an idea for why?

Thanks.

// this one just does not move to the center ??????

DataGridViewColumn column1 = portCodeGrid.Columns[1];

column1.HeaderText = "Port";

column1.AutoSizeMode = DataGridViewAutoSizeColumnMode.Fill;

column1.Resizable = DataGridViewTriState.False;

DataGridViewColumn column2 = portCodeGrid.Columns[2];

column2.HeaderText = "Color";

column2.ReadOnly = true;

column2.Resizable = DataGridViewTriState.False;

DataGridViewColumn column3 = portCodeGrid.Columns[3];

column3.HeaderText = "Code";

column3.AutoSizeMode = DataGridViewAutoSizeColumnMode.Fill;

column3.Resizable = DataGridViewTriState.False;

}