title: POI setting Cell Background to a Custom Color
body: <p>I want to set custom color to a cell's background.<br>
  I use <code>HSSFWorkbook</code> (can't use anything else).</p>
  
  <pre><code>HSSFPalette palette = aWorkBook.getCustomPalette();             
  Color col = new Color(backgroundColor);                     
  HSSFColor myColor  = palette.addColor((byte) 10, (byte) 11, (byte) 12); 
  </code></pre>
  
  <p>I get this error: <code>java.lang.RuntimeException: Could not find free color index</code></p>