LOL. When I read the heading I was actually going to suggest a Bella... then I see all the Montaigne love and feel like I am a horrible traitor! I agree that the Montaigne is perfect for everything, obviously, but just thought that something that is a bit better over the shoulder (like the Bella) might be a bit more convenient when being shlepped onto the plane and all.
As for colour, I wouldn't have a problem with the Carmino in terms of professionalism (I think it is a nice pop of colour but still not over the top) but I would worry that it might get damaged on the plane or being set down in not-so-perfect places, which is why I tend to travel with darker colours. Ink sounds pretty perfect for all of that, BTW...