Question about herpa factory models

Hi there,
I have an old Herpa A320 Ansett and I was thinking to have fun with it making some modifications. For first before start I was trying to understand how Herpa models are built, I mean that there are parts who are painted and there are parts who have decals applied, aren't you?
For example in the following Cyprus A320 the lower grey of the fuselage will be removed with the nail polish remover?


In this British midland A330 with the nail polish remover I'll remove from the fuselage only windows, doors and logo but the blu part of the fuselage will remain?


thank you in advance
G