There are no surface-to-surface lighting features in Poser other than IDL (P8+ only) and Gather, so I don't know what you could possibly mean by "figure out this color bleed".

A mesh's shader can only alter how that mesh appears or how things are seen through that mesh. It cannot alter how things are seen or lit around that mesh, except where a nearby mesh has a Gather node on it, or if IDL is enabled.

I understand why you can't use a second mesh, but that is the only way. Poser atmosphere does not use the color of objects and that (atmosphere) is the only feature that causes empty (meshless) sections of space to glow.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)