    private void button2_Click(object sender, EventArgs e)
        {
         // obtain new front color from text boxes
        frontColor = Color.FromArgb( Convert.ToInt32(textBox2.Text ), Convert.ToInt32( textBox3.Text ),Convert.ToInt32( textBox4.Text ), Convert.ToInt32( textBox5.Text ) );
        Invalidate(); // refresh Form
        }
