Paleta de Colores

Dejo el código necesario para mostrar en pantalla, un conjunto de cuadros con distintos colores

import java.awt.Color;

import java.awt.Container;

import java.awt.Dimension;

import java.awt.FlowLayout;

import java.awt.Graphics;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JPanel;

@SuppressWarnings("serial")

public class paletaColores extends JFrame implements ActionListener{

JButton boton;

JPanel panel;

public static void main(String[] args) {

paletaColores marco = new paletaColores();

marco.setSize(220, 400);

marco.setTitle("Tablero del gato");

marco.dibujaGUI();

marco.setLocationRelativeTo(null);

marco.setVisible(true);

}

public void dibujaGUI() {

setDefaultCloseOperation(EXIT_ON_CLOSE);

Container ventana = getContentPane();

ventana.setLayout(new FlowLayout());

panel = new JPanel();

panel.setPreferredSize(new Dimension(220,320));

panel.setBackground(Color.white);

ventana.add(panel);

boton = new JButton("Haz click");

ventana.add(boton);

boton.addActionListener(this);

}

public void actionPerformed(ActionEvent evento) {

Graphics papel = panel.getGraphics();

papel.drawRect(20, 20, 40, 40);

papel.setColor(Color.black);

papel.fillRect(20, 20, 40, 40);

papel.drawRect(80, 20, 40, 40);

papel.setColor(Color.blue);

papel.fillRect(80, 20, 40, 40);

papel.drawRect(140, 20, 40, 40);

papel.setColor(Color.cyan);

papel.fillRect(140, 20, 40, 40);

papel.drawRect(20, 80, 40, 40);

papel.setColor(Color.DARK_GRAY);

papel.fillRect(20, 80, 40, 40);

papel.drawRect(80, 80, 40, 40);

papel.setColor(Color.gray);

papel.fillRect(80, 80, 40, 40);

papel.drawRect(140, 80, 40, 40);

papel.setColor(Color.green);

papel.fillRect(140, 80, 40, 40);

papel.drawRect(20, 140, 40, 40);

papel.setColor(Color.LIGHT_GRAY);

papel.fillRect(20, 140, 40, 40);

papel.drawRect(80, 140, 40, 40);

papel.setColor(Color.magenta);

papel.fillRect(80, 140, 40, 40);

papel.drawRect(140, 140, 40, 40);

papel.setColor(Color.orange);

papel.fillRect(140, 140, 40, 40);

papel.drawRect(20, 200, 40, 40);

papel.setColor(Color.pink);

papel.fillRect(20, 200, 40, 40);

papel.drawRect(80, 200, 40, 40);

papel.setColor(Color.red);

papel.fillRect(80, 200, 40, 40);

papel.drawRect(140, 200, 40, 40);

papel.setColor(Color.white);

papel.fillRect(140, 200, 40, 40);

papel.drawRect(10, 260, 40, 40);

papel.setColor(Color.yellow);

papel.fillRect(20, 260, 40, 40);

}

}