Autralia huh? hmmmmm ...
An archaic meaning for the word currency, according to the Oxford English dictionary is : a native born Australian! So : Currency?
For a bay-colored horse, of course BOTNAY BABY (Mis-spelled on purpose so it can be registered, thank you).
For a black horse : Dark Knight
For a filly : "Quite the Lass" or "Big Bad Broad" (if your friend's mind works that way.) ...
Then I also like, for the trouble they will cause announcers, "Out In Front" and "WINNER"
wow