Devi usare l'istruzione JColorChooser del package javax.swing.
Io uso la versione di java 1.3.
Per consultare le classi vai all'indirizzo:
http://java.sun.com/products/jdk/1.2...api/index.html

Ecco un esempio:
import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
public class ColorDialogTest
{
public static void main(String args[])
{
JFrame frame = new ColorFrame();
frame.show();
}
}

class ColorFrame extends JFrame
{
public ColorFrame()
{
setTitle("ColorTest");
Toolkit toolkit = Toolkit.getDefaultToolkit();
Dimension d = toolkit.getScreenSize();
int x = d.width / 4;
int y = d.height / 4;
setBounds(x, y, d.width / 2, d.height / 2);

addWindowListener(
new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
System.exit(0);
}
});

Container contentPane = getContentPane();
JButton colorButton = new JButton("Colore");
JPanel panel1 = new JPanel();
panel1.add(colorButton);
contentPane.add(panel1, BorderLayout.SOUTH);
panel2 = new JPanel();
contentPane.add(panel2, BorderLayout.CENTER);

colorButton.addActionListener(
new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
//Per JColorChooser vedere Api Java
//http://java.sun.com/products/jdk/1.2/docs/api/index.html
panel2.setBackground(JColorChooser.showDialog
(ColorFrame.this, "Scegli un colore",Color.yellow));
}

});

}
private JPanel panel2;
}