I don't think that we can figure out what is going on in conscious colour perception just by phenomenological introspection. We need to know about brain mechanisms as well. We need to figure out what information is present in the mechanisms that constitute conscious colour perception.

The 'phenomenal concept' issue is rather different, I think. Here the question is whether there are concepts of experiences that are made available to subjects solely in virtue of their having had those experiences themselves. Is there a way of thinking about seeing something red, say, that you get from having had those experiences, and so isn't available to a blind person?

In truth a clear-headed physicalist shouldn't be thinking any of these dualist thoughts. If pains are one and the same as C-fibres firing, then there really isn't any possibility of having 'one' without the 'other'. Once you properly appreciates physicalism, this dissociation should cease to appear possible - C-fibres with pains should strike you as no more possible than squares without rectangles.

Schrödinger's cat has a 50% quantum chance of coming out of the box alive and a 50% quantum chance of coming out dead. If you got in the box with it, the same would apply to you. So you really don't want to do that.

Natural selection has ensured that each species achieves the requisite effect somehow, but it doesn't care, so to speak, how the trick is done.

Philosophers sometimes also use 'reductionist' more strictly, to mean 'type-identities' between mental and physical categories, and to exclude 'non-reductive physicalisms' like metaphysical functionalism.

If there is such a simple argument for physicalism, how come everybody hasn't always been a physicalist? That's a good question, and there is a good answer. The 'causal completeness of physics' wasn't widely accepted until recently.