Randomly assign different materials to the instances to introduce variations.
It works the same way as applying a material to a component or a group in SketchUp: only the blank faces in the components will receive the material. If faces already have a material, their material cannot be replaced.
When using "Render-only", this feature is supported by V-Ray and Thea, but not Enscape at this time.
Random materials (Right) introduce more diversity compared to having a single material (Left).
Click on the icon to select materials in a list, or click the icon to pick the materials directly in the viewport.