Check again the example, it explictly states: "The text returned in *buf is colour coded, so you need to use tag_remove() (see section 5.20.1) to get printable text."
Also, please remember that using the ua_outop(...) function is not really the best way to go: parsing the cmd structure is much more reliable and effective, as it gives you access to each and every information related to instruction, operands & more. Please check the ua.hpp header file ;)