public class MainFrame extends JFrame {

	public MainFrame() {
		contentPane = this.getContentPane();
                ...
                BaseFactory factory = AbstractFactory.getFactory(id);
		dpanel = factory.createDrawPanel();
		dpanel.setBackground(Color.RED);
		contentPane.add(dpanel);
        }

	private Container contentPane;
	private DrawPanel dpanel;
}

public class MainFrame extends JFrame {

	public MainFrame() {
		contentPane = this.getContentPane();
                ...
		menuAndActions(...);
        }

	private void menuAndActions(...) {
		...
		Action drawLineAction = new AbstractAction(...) {

			public void actionPerformed(ActionEvent arg0) {
				BaseFactory factory = AbstractFactory.getFactory(id);
				dpanel = factory.createDrawPanel();
				dpanel.setBackground(Color.RED);
				contentPane.add(dpanel);
			}
		};
		...
	}

	private Container contentPane;
	private DrawPanel dpanel;
}

public void actionPerformed(ActionEvent arg0) {
        dpanel.setBackground(Color.BLUE); 
}

contentPane.setVisible(false);
contentPane.setVisible(true);

contentPane.validate();