Get the JFrame by getting the root of a component : SwingUtilities « Swing « Java Tutorial

1. Java Tutorial
2. Swing
3. SwingUtilities

import java.awt.Color;
import java.awt.Component;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;

public class Main extends JFrame {
  public Main() {
    this.setSize(400, 100);
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    this.setLayout(new FlowLayout(FlowLayout.CENTER));
    JButton button = new JButton("Change Frame Color");
    button.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        Component component = (Component) e.getSource();
        JFrame frame = (JFrame) SwingUtilities.getRoot(component);
        frame.getContentPane().setBackground(Color.RED);
      }
    });
    this.getContentPane().add(button);
  }
  public static void main(String[] args) {
    new Main().setVisible(true);
  }
}