Thread: Adding background to frame

I couldnt add background color to frame although there is no errors showing.
hope there would be someone who can guide me as soon as possible
And the name of the class is a malay word but it means color

import java.awt.*;
import java.awt.event.*;
import java.awt.event.ActionListener;
import javax.swing.*;

public class Warna extends JFrame implements ActionListener {

private JButton b1;

Warna() {
//super(str);
setSize(310, 300);
setVisible(true);
setLayout(new FlowLayout());
//Label lname = new Label("MyFrame");
//JButton
b1 = new JButton("RED");
add(b1);

b1.addActionListener(this);

//ButtonHandler bh = new ButtonHandler()
}

public void actionPerformed(ActionEvent e) {
String a = e.getActionCommand();


Color c1 = getBackground();
if (a.equals("red")) {
c1 = Color.RED;
}

setBackground(c1);
repaint();


}

public static void main(String[] args) {
Warna w = new Warna();
}
}