For the record, no one in Italy refers to Fiorentina as "la viola". It's "i viola" (the mauves, as in the players wearing a mauve shirt). That's another recurrent misinterpretation of Italian football terminology by foreigners, along with the habit of calling the two milanese teams "Inter Milan" and "AC Milan", when we only use "Milan" and "Inter".
Alternatively Juventus gets also called "la Vecchia Troia". Do not hesitate to use the term loosely if you happen to attend a game at Delle Alpi. Say it loudly and proudly : "forza Vecchia Troia!".