title: NPOI: how to use custom XSSFColor in conditional formatting?
body: <p>What I have:</p>
  
  <pre><code>var sheetCf = sheet.SheetConditionalFormatting;
  var rule = sheetCf.CreateConditionalFormattingRule("A2&gt;0");
  var fill = rule.CreatePatternFormatting();
  
  fill.FillBackgroundColor = IndexedColors.Red.Index;
  fill.FillPattern = (short)FillPattern.SolidForeground;
  </code></pre>
  
  <p>How can I set Custom color for background?</p>