In the Class: BuildingButton > UpdateBuildingPreview
The lecture line looks like this:
buildingRendererInstance.material.SetColor("_BaseColor", color);
In your project (like in mine) it might need to be this:
buildingRendererInstance.material.SetColor("_Color", color);
For one step further, if you’re changing just the Color attribute, you can set it directly:
buildingRendererInstance.material.color = color;
Hope this helps 