The whole house model is ONE model.
Just as an eave, roofline, tree are models, and may have RBG or BRG elements, the models themselves always have only one color mode (RGB, BRG,RBG,)
I believe the preview will look funky if not all elements are RGB, but the actual output will be ok.
It works for me with RGB and RBG elements mixed in my WHM when I output to lights.