title: How to set background color of a View
body: <p>I'm trying to set the background color of a View (in this case a Button).</p>
  
  <p>I use this code:</p>
  
  <pre><code>// set the background to green
  v.setBackgroundColor(0x0000FF00 );
  v.invalidate();
  </code></pre>
  
  <p>It causes the Button to disappear from the screen.   What am I doing wrong, and what is the correct way to change the background color on any View?</p>
  
  <p>Thanks.</p>