I don’t know about Australia, but in the countries i have heard about with compulsory voting, it’s totally legal to vote blank, i.e. not actually vote for anyone. You just have to go to the polling station and put your blank ballot in the box.
So you’re (if i’m not mistaken) not forced to vote for a party you don’t agree with.
You can also just pause it and change filament manually.
Just remember to push through some of the filament until the color comming out is right.