Argh, since I already spent the time putting together a reply to a post that was apparently deleted just now, I'm going to post it anyway. Hopefully this post will come up the next time someone searches for this topic.
Effect of palette read on $2007 buffer
Intentionally clear description of palette entries and access
Code illustrating color while PPU is off
Fully expanded mapping of the $3Fxx address is mapped to the 28 physical palette entries
Palette memory behavior
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