public class DemoTableLayoutPanel : TableLayoutPanel
{
    protected override void OnCellPaint(TableLayoutCellPaintEventArgs e)
    {
        base.OnCellPaint(e);

        Control c = this.GetControlFromPosition(e.Column, e.Row);

        if ( c != null )
        {
            Graphics g = e.Graphics;

            g.DrawRectangle(
                Pens.Red, 
                e.CellBounds.Location.X+1,
                e.CellBounds.Location.Y + 1,
                e.CellBounds.Width - 2, e.CellBounds.Height - 2);

            g.FillRectangle(
                Brushes.Blue, 
                e.CellBounds.Location.X + 1, 
                e.CellBounds.Location.Y + 1, 
                e.CellBounds.Width - 2, 
                e.CellBounds.Height - 2);
        };
    }
}