Layering materials for combined effect

not seeing how to do this
for instance, is it possible to create a material that is the intended Finish, Reflectivity, and Transparency (no Color) and then lay this material definition on top of many Color only materials for the combined effect?
This to enable editing a single “Finish” material that effects all Color materials where it is used in the model?

Not with the regular materials, and only for the Raytraced mode.

You should look into using GhShaderNodes with the Cycles XML material. A search for those with results ordered by recent date should give you enough info to get started.

Another way is to work with Rhino custom material. Then create a script to generate all material color variations you seek.