Assign material parameter to family geometry

I am looking to create a new family via Rhino/Grasshopper for use in Revit. I am using the BREP Component Family form to generate geometry and then feeding that into a New Component Family. What is the proper way to assign a parameter to drive the material of the geometry. I have tried creating a new material definition and adding that to the material Node of the BREP, but the parameter doesn’t exist in the family when loaded into Revit.

The closest I have found to be able to control portions of geometry is to create new subcategories and assign to the various BREPs that way. Is this possible yet?

Are you doing an Instance or Type Material?

Instance being that you can select the individual family instance in the Project and change its material to one in the project.

Type based being in the Family and assigned to a Type there, any changes being made in the Family by its respective type.

The bottom line is you are going to need to associate the Elements Material Family Parameter with a newly created material family/shared parameter, either Type or Instance.

Which is only available via the API or manually at this time.