Accessing HDRP LayerLit layer at runtime.

I want to access the Material in a layer of HDRP/LayeredLit Shader from a script. Specifically, I would like to change the Layer1 / Surface inputs / base map / color. I have looked through Materials documentation, and all my editor suggestions for fields and methods of material. I can’t find anything about a layer.

The property “_BaseColor1” sets the Layer1 Color