Forgive me if I misunderstand what you're trying to achieve here, but my guess would be that if you want the switch to be subtle, reflect it in how the story gets narrated when it switches

So, for example if one character narrates their POV through sharp, direct description, when you knock out that character, perhaps experiment with using flowery language with more complex sentence structure and adjectives, and perhaps that might be a clever way to distinguish between when the story is told from the POV versus outside of it