This is a multi-building farm with stone walls and slate roofs. The STL’s are available here: https://cults3d.com/:1947056.
 A very similar but not identical farm build is detailed by “Storm of Steel” here: https://youtu.be/umlfubM83-Y?si=A3jWVUSzHIA2qILR. The main difference is that his has brick buildings where this one is made of stone walls. 
Prime white, then base coat in   Celestra Grey  
Pick out random stones in various shades of brown and grey.    Dawnstone 
  XV-88  
  Skrag Brown  
  Doombull Brown  
  Balor Brown  
  Mechanicus Standard Grey  
  Dawnstone  
Apply a wash of   Agrax Earthshade  over all the stonework to unify it.
Paint the woodwork in green   Warboss Green  
Paint the tile roofs in   Mechanicus Standard Grey  
Highlight the woodwork with a dry brush of a lighter green and dry brush the tiles with   Dawnstone  
Apply the same stone painting technique to HO scale embossed plasticard mounted on a thicker plasticard base for strength.
Weather the tile roofs with   Green Ochre  ,   German Fieldgrey WWII  , and   Buff  as described in the video.