trying to change the background color of a JPanel but it has no effect

I don't think JPanel has a constructor with the specified Color

Make sure you call setOpaque(true) on it

ya i've already tried both of those..

This simple code (see below) runs for me and shows whatever
color I set to JPanel.
Please, run this one - I'm sure it will run for you.
If it runs then post your code which does not show color to you.

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

public class JPanelColor extends JFrame {
    JPanel p;

    public JPanelColor(){
        p = new JPanel();
        p.setBackground(Color.BLUE);
        this.getContentPane().add(p);
        this.setSize(100,100);
        this.show();
    }

    public static void main(String [] args){
        new JPanelColor();
    }

}

I figured it out.  The problem was that I was using the repaint() method inside of my panel to draw on the panel using a double buffer graphics object and that was overriding my call to setBackground with its own background.