The Diffuse_Color and Diffuse_Value are the exposed inputs to an internal, invisible Diffuse node, which is then connected to an internal, invisible giant Color_Math:Add which outputs the almost-final color that goes into the transparency mixer. Using this is identical to explicitly using a Diffuse node connected to Alternate_Diffuse. If transparency is not involved, it's also identical to using a Diffuse node in any of the other channels equivalent to Alternate_Diffuse. They all go to the transparency mixer as equals.

The Specular_Color, Specular_Value, and Highlight_Size are the exposed inputs to an internal, invisible Specular node, which is then connected to an internal, invisible giant Color_Math:Add which outputs the almost-final color that goes into the transparency mixer. If transparency is not involved, it's also identical to using a Specular node in any of the other channels equivalent to Alternate_Diffuse. They all go to the transparency mixer as equals.

As I mentioned (and don't really want to explain in detail) each of the almost-equivalent channels that do what they're told to do are not quite identical. They influence the transparency mixer (final stage of the shader engine) in different ways and are hooked up to other things internally in different ways.

The Translucence channel will (if correctly wired) reverse the normal used in lighting calculations attached to it.

The Reflection_Color channel will be further modulated by light and/or the diffuse color if you turn on those Reflection_Lite_Mult or Reflection_Kd_Mult. This is so non-obvious that I just make a simple rule for the less-than-expert population - don't use those.

The Reflection_Color and Specular_Color influence the final transparency mixer in non-obvious ways. Again - not documented, not clear on the math, and just not necessary, so I steer clear when transparency is involved. I prefer to explicitly see every step and just have the Poser surface node be nothing but a dumb adder.

Whenever there's a pair XYZ_Color and XYZ_Value, they are internally and invisibly multiplied together.

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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)