public HighlightingDefinition AddSpan(string startExpression, string endExpression, FontOptions options)
 {
     return AddSpan(startExpression, endExpression, options.ToHighlightingColor());
 }
 public HighlightingDefinition AddRule(string expression, FontOptions options)
 {
     return AddRule(expression, options.ToHighlightingColor());
 }