If you want to change the BackColor of a column, you would typically use the CellAppearance property on that column.

If you want the color in this case to be tied to the fact that the column is fixed, then I recommend using the FixedCellAppearance property on the override object. That way if you decide to add another fixed column or change which column is fixed, the fixed columns will always pick up this appearance without you having to change the code.