Wow, cool rural place. First question; are you trying to avoid the obvious choice - an authentic barn deep red? It can be done tastefully if it's the right red (not too bright) and is combined with white and gray accents. Shades of gray would work too, but definitely white trim. You might consider doing the lower half a shade darker than the upper story too for interest and scale. There's a lot of possibilities with a house this large, especially the way it is designed as two separate buildings united by a covered walkway. What color did you envision when the house was designed?

Why not go with Barn Red?

Perhaps a dark warm grey would be nice if your don't go with the obvious red (although I love it). If you did the buildings in dark grey, how about red accents for the garage doors and front door. And I like the idea of making the building connecting the house to the garage a light grey because it would give some contrast. You don't want a flat palette in the end with a house so big! Or perhaps using the red? Definitely do white trim.
It looks like your roof is grey? Is that right ?