"Color bleeding" is the correct term for the effect, I believe you're right about that. It's a consequence of the diffuse interreflection. We used to have to use Gather nodes in materials to get this to happen in Poser, and it always looked bad.

Here's a demo. Crappy quality, but quick. I cranked up the Diffuse_Value on the balls to make it more obvious.

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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)