Can someone tell me why I need to create a raw query to be able to search with Escape()?

This brings back 0 results:

if (!string.IsNullOrEmpty(criteria.Colour))
{
  query = query.And().Field("colour",  criteria.Colour.Escape());
}

But if I extract the RAW query and run it... It works:

string stringToParse = query.ToString();
int indexOfPropertyValue = stringToParse.IndexOf("LuceneQuery:") + 12;
string rawQuery = stringToParse.Substring(indexOfPropertyValue).TrimEnd('}');
var response = index.Searcher.CreateQuery("content").NativeQuery(rawQuery).Execute(QueryOptions.SkipTake((criteria.CurrentPage - 1) * criteria.PageSize, criteria.PageSize));