How to do syntaxhighlighting for terminal rules in Xtext? - syntax-highlighting

Question

I would like to do custom syntaxhighlighting in xtext. I would like to highlight everything that matches a terminal rule in a specific color.
For example my terminal rule:
terminal MYRULE:
('ab'|'2')*
;
I would like to color the everything like a comment what matches this terminal rule.
I tired the following:
package org.xtext.example.mydsl.ui;
import java.util.regex.Pattern;
import org.eclipse.xtext.ide.editor.syntaxcoloring.HighlightingStyles;
import org.eclipse.xtext.ui.editor.syntaxcoloring.DefaultAntlrTokenToAttributeIdMapper;
public class STAntlrTokenToAttributeIdMapper extends DefaultAntlrTokenToAttributeIdMapper {
private static final Pattern QUOTED = Pattern.compile("(?:^'([^']*)'$)|(?:^\"([^\"]*)\")$", Pattern.MULTILINE);
private static final Pattern PUNCTUATION = Pattern.compile("\\p{Punct}*");
#Override
protected String calculateId(String tokenName, int tokenType) {
System.out.println("token = " + tokenName);
if ("MYRULE".equals(tokenName)) {
return HighlightingStyles.COMMENT_ID;
}
if(QUOTED.matcher(tokenName).matches()) {
return HighlightingStyles.KEYWORD_ID;
}
if("RULE_STRING".equals(tokenName)) {
return HighlightingStyles.STRING_ID;
}
if("RULE_INT".equals(tokenName)) {
return HighlightingStyles.NUMBER_ID;
}
if("RULE_ML_COMMENT".equals(tokenName) || "RULE_SL_COMMENT".equals(tokenName)) {
return HighlightingStyles.COMMENT_ID;
}
return HighlightingStyles.DEFAULT_ID;
}
}
I see the print for "MYRULE". The code is accepted from the editor. But the special code part is not highlighted.
Of course the rule is just an example and not part of the DLS I am working on. But I can't tell details about my DSL.