how to change color of titlebar in java

import javax.swing.*;
public class ChangeTitleBarColor{
    public static void main(String[]args){
    JFrame f = new JFrame();
    f.setUndecorated( true );
    f.getRootPane().setWindowDecorationStyle( JRootPane. COLOR_CHOOSER_DIALOG );
    f.setVisible(true);
    f.setSize(300,100);

    }
}

pls explain....And it shows green color...what if i want some other color

import javax.swing.*;
public class ChangeTitleBarColor{
    public static void main(String[]args){
    JFrame f = new JFrame();
    f.setUndecorated( true );
int x=3;// use x value from 1 to 8
    f.getRootPane().setWindowDecorationStyle( x);
    f.setVisible(true);
    f.setSize(300,100);

    }
}