Where is vertex color for standin (Proxy) with operators to override?

[louism777]

I'm using Maya for rendering.

I have a proxy or standin grass ready and single shader or material ready to assign proxy. I just learned how operators work for proxies to override anything to make it interactive.

I learned how to put shader = 'name for material' under Set Parameter and with that I can add textures like base color, normal, ect. But what is missing is where is vertex color? I tried to put userDataColor (did put the name in attribute "colorSet0" from previous material ready) and still nothing. Usually I checked "Export Vertex Colors" under Shape rollout but for proxy it's not there and don't see any option to override.

Any help would much appreciate it and thank you!