With the 7th ed Codex, I decided to update my Grey Knights:
Grey Knight HQs:
Both models are magnetized. The top picture is a Librarian & Kaldor Draigo, the bottom picture has them swapped as Grand Masters.
As you can see, they are magnetized to swap out weapons.
Terminators & Paladins:
I tried to avoid making a clear distinction between them as I have lists that are all Terminators, or a mix of Paladins & Termies. In my mixed lists, I distinguish them by which units have Apothecaries/more Psycannons.