I agree the possibilities are endless Gerda and I do think that the windows should match the colour of the doors but that is just my opinion and not based on any factual evidence.
I really like the dark green unpainted roof.....it could either be a mistake or someone has removed the white paint off as I don't think it would be that hard to do compared to removing paint from an actual smurf figure.
Either way it makes a nice variation to the others I think
I also still don't have any cottages with the grey windows or doors yet (as far as I know).....I will have to keep a look out for some of those as they seem to be out there...just not yet in my collection though.
Dyar