Filter for RGB separation

The thing here is that there is no absolute standard of where one band ends and another band begins, and depending on the application there's a huge number of possible choices that make sense.

In this regard, one common system that might suit what you're looking for is the Wratten system for astrophotography (where sharply tuned colour filters tend to be quite useful), and they come in quite a handful:

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If what you're looking for is strict bandpass filters at bands that one can recognize as red, green and blue, then these MaxMax XNiteBP filters probably fit the bill,

with the caveat that there will be some cyan and yellow light sources that it just doesn't see.

So: within the vague confines of the question as you've posed it, there's plenty of interesting solutions, each with its own tradeoffs, and with its own underlying physical mechanisms. Beyond that it's hard to say anything else.