title: Changing the custom-attrs.xsl file in DITA did not change my background-color of table column headers. how do I change it, then?
body: <p>I expected that changing the <code>trgoup.thead</code> element in <code>custom-attrs.xsl</code> with <code>background-color</code> would change the table column head background color.</p>
  <p>But the background of the table column heads did not change. I put the file in both <code>fo/xsl/</code> and <code>attrs/</code>. What am I doing wrong?</p>