Response to: How to change the color of a button on btnclick event

public void single_button_Click(object sender, EventArgs e)
  {
    Button btn = (Button)sender;
    if (btn.BackColor == Color.Red)
    {
      btn.BackColor = SystemColors.Control;
    }
    else if (btn.BackColor == SystemColors.Control)
    {
      btn.BackColor = Color.Red;
    }
  }