You can actually customize the labels in OO.ui.confirm() too:
OO.ui.confirm( '...', { actions: [ { action: 'accept', label: 'Yes!', flags: 'primary' }, { action: 'reject', label: 'No…', flags: 'safe' } ] } ).done( function ( confirmed ) { ... } );
Make sure to keep the `action: 'accept'` and `action: 'reject'` (the dialog uses this to make the two buttons do things), the other pieces can be changed.