/* documentation comment */
DocCommentElement:
   text = ( SL_DOC_COMMENT | ML_DOC_COMMENT )

terminal ML_DOC_COMMENT: '<#' -> '#>';
terminal SL_DOC_COMMENT: '#' !('\n'|'\r')* ('\r'? '\n')?;

public class MyHighlightingConfiguration extends DefaultHighlightingConfiguration
{
   // provide ID strings for the highlighting calculator
   public static final String DOCUMENTATION_COMMENT_ID = "documentation comment";
   
   @Override
   public void configure(IHighlightingConfigurationAcceptor acceptor)
   {
      // let the default implementation first do the job
      super.configure(acceptor);
      
      // here our custom styles are used
      acceptor.acceptDefaultHighlighting(DOCUMENTATION_COMMENT_ID, "Documentation comment", documentationCommentTextStyle());
   }
   
   public TextStyle documentationCommentTextStyle() {
      TextStyle textStyle = defaultTextStyle().copy();
      textStyle.setColor(new RGB(63, 95, 191)); // default Eclipse JavaDoc color
      return textStyle;
   }
}

public class MySemanticHighlightingCalculator implements ISemanticHighlightingCalculator
{

   @Override
   public void provideHighlightingFor(XtextResource resource, IHighlightedPositionAcceptor acceptor)
   {
      if (resource == null || resource.getParseResult() == null)
         return;

      INode root = resource.getParseResult().getRootNode();
      for (INode node : root.getAsTreeIterable())
      {
         if (node.getSemanticElement() instanceof DocCommentElement)
         {
            acceptor.addPosition(node.getOffset(), node.getLength(),
                  MyHighlightingConfiguration.DOCUMENTATION_COMMENT_ID);
         }
      }
   }
}

for (ILeafNode node : root.getLeafNodes())
 {
         if ( node.getSemanticElement() instanceof DocCommentElement && !node.isHidden())
         {
            acceptor.addPosition(node.getOffset(), node.getLength(),
                  MyHighlightingConfiguration.DOCUMENTATION_COMMENT_ID);
         }
}