A couple of coats of shellac to give the card strength (yes you are correct Zak with what to use) and then a first coat of colour to represent the plaster.
Yes for the eagle eyed, one is off white and the other is more yellow, the last photo is the beams on the outside of the house black for the white and brown for the yellow.

Corner sections on the yellow building and first 2 sections of timber - think its going to be a longgggggg job       

Good progress Martin.

Door section made and fitted to the round house.  Both now primed and a start made on adding wood cladding to the middle section of the top, the bottom will be stone.
Deciding at the moment to make it into a living accommodation with windows etc or make it a look out post with a wood roof and space to look out from         

This should keep you busy for a while.

If it keeps him quiet, it's all good.
Sorry Martin.
An interesting, mind perplexing build.