Access material of visualarq objects in grasshopper

Hi I would like to create wall styles through grasshopper and be able to assign materials to the individual layers. Is there a way to do so?

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I was wondering if I could access the guid of the individual wall layers in a wall style and assign the material to the wall layer. However, it shows that the array is empty when I try to retrieve the wall layers using the va.GetWallLayers() command. Could I get help with this?