The Lua mode in GeSHi isn't that great; it doesn't even highlight long strings out of the box*. On the other hand, it exists and it works moderately well; if you don't mind shelling out to PHP it might be worth a try.If you don't mind the syntax highlighter being in another language, you could try Geshi or Pygments.
- Peter Odding* http://stackoverflow.com/questions/3659606/lua-long-strings-not-displaying-correctly-using-geshi-syntax-highlighting