title: JFrame.setBackground() not working -- why?
body: <pre><code>    JFrame mainFrame = new JFrame();
      mainFrame.setSize(100, 100);
      mainFrame.setBackground(Color.CYAN);
      mainFrame.setVisible(true);
  </code></pre>
  
  <p>My intent is to create a window with a cyan background. What is wrong with this? My window doesn't get cyan, as I'd expect!</p>
  
  <p>Also, could anyone point out why I seem to have all the colors in duplicate (there's a Color.CYAN and a Color.cyan). Is there any difference at all between the two? Maybe the older one was a constant from before there were enums in Java and the second one is from the Enum?</p>
  
  <p>Thanks</p>