Windows forms application datagridview background color

protected override void PaintBackground(Graphics graphics, Rectangle clipBounds, Rectangle gridBounds)
        {
            base.PaintBackground(graphics, clipBounds, gridBounds);
            Rectangle rectSource = new Rectangle(this.Location.X, this.Location.Y, this.Width, this.Height);
            Rectangle rectDest = new Rectangle(0, 0, rectSource.Width, rectSource.Height);

            Bitmap b = new Bitmap(Parent.ClientRectangle.Width, Parent.ClientRectangle.Height);
            Graphics.FromImage(b).DrawImage(this.Parent.BackgroundImage, Parent.ClientRectangle);


            graphics.DrawImage(b, rectDest, rectSource, GraphicsUnit.Pixel);
            SetCellsTransparent();
        }


        public void SetCellsTransparent()
        {
            this.EnableHeadersVisualStyles = false;
            this.ColumnHeadersDefaultCellStyle.BackColor = Color.Transparent;
            this.RowHeadersDefaultCellStyle.BackColor = Color.Transparent;


            foreach (DataGridViewColumn col in this.Columns)
            {
                col.DefaultCellStyle.BackColor = Color.Transparent;
                col.DefaultCellStyle.SelectionBackColor = Color.Transparent;
            }
        }