Using random in java

Hey guys I came a cross with a little problem while using java, I don't have enough experience into this language and I am trying to figure it out how to use random, here's my code, i'd appreciate a little help:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.Random;

public class Colorshape extends JFrame implements ActionListener {

    private JButton Morered, Lessred;
    private JButton Moreblue, Lessblue;
    private JButton Moregreen, Lessgreen;
    private JButton Randombutton;
    private int red = 150;
    private int blue = 150;
    private int green = 150;

    Random rbg = new Random();
    int R = (int) (Math.random() * 256);
    int B = (int) (Math.random() * 256);
    int G = (int) (Math.random() * 256);
    Color myrandomcolor = new Color(R, B, G);

    private Color randomcolour = myrandomcolor;

    private JLabel r, b, g;
    private JPanel panel;

    public static void main(String[] args) {
        Colorshape demo = new Colorshape();
        demo.setSize(900, 400);
        demo.createGUI();
        demo.setVisible(true);
    }

    private void createGUI() {
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        Container window = getContentPane();
        window.setLayout(new FlowLayout());
        panel = new JPanel();
        panel.setPreferredSize(new Dimension(400, 300));
        panel.setBackground(Color.white);
        panel.setVisible(true);

        Morered = new JButton("More red");
        Lessred = new JButton("Less red");
        Moreblue = new JButton("More blue");
        Lessblue = new JButton("Less blue");
        Moregreen = new JButton("More green");
        Lessgreen = new JButton("Less green");
        Randombutton = new JButton("Random");

        r = new JLabel("red: " + red);
        b = new JLabel("blue: " + blue);
        g = new JLabel("green: " + green);

        window.add(r);

        window.add(Morered);
        Morered.addActionListener(this);

        window.add(Lessred);
        Lessred.addActionListener(this);

        window.add(b);

        window.add(Moreblue);
        Moreblue.addActionListener(this);

        window.add(Lessblue);
        Lessblue.addActionListener(this);

        window.add(g);

        window.add(Moregreen);
        Moregreen.addActionListener(this);

        window.add(Lessgreen);
        Lessgreen.addActionListener(this);

        window.add(Randombutton);
        Randombutton.addActionListener(this);

        window.add(panel);
    }

    @Override
    public void actionPerformed(ActionEvent event) {
        Object source = event.getSource();

        if (source == Morered) {
            red = red + 10;
        } else if (source == Lessred) {
            red = red - 10;
        } else if (source == Moreblue) {
            blue = blue + 10;
        } else if (source == Lessblue) {
            blue = blue - 10;
        } else if (source == Moregreen) {
            green = green + 10;
        } else if (source == Lessgreen) {
            green = green - 10;
        }
        if (source == Randombutton) {
        }

        Graphics paper = panel.getGraphics();
        Color cr = new Color(red, 0, 0);
        paper.setColor(cr);
        paper.fillRect(20, 20, 80, 50);
        Color cb = new Color(0, 0, blue);
        paper.setColor(cb);
        paper.fillRect(150, 20, 80, 50);
        Color cg = new Color(0, green, 0);
        paper.setColor(cg);
        paper.fillRect(280, 20, 80, 50);
        Color n = new Color(red, blue, green);
        paper.setColor(n);
        paper.fillOval(120, 100, 150, 150);
    }

}