"There are three green ones, then a blue one."
This sort of thing confuses me. Surely 'then' is not a conjunction.
Possibly some prescriptivist grammars may say you "should" say 'I got up AND AFTERWARDS I had breakfast', but most speakers would say either 'I got up, then I had breakfast' or some inversion of the clauses, such as 'Before having breakfast I got up. In the first case, I don't see how you could describe 'then' as anything but a conjunction - though maybe it's more common in an informal context.
I'm open, as ever, to argument, but I've never before come across the assertion that 'then' can't behave as a conjunction.