Please post pictures. I assume you are putting the galvalume on the roof. Will it be the silver color? What kind of rock are you using and what color is the wood? Impossible to give you good color options without more information. But without any information, I would go with dark grey for a contemporary look.

Actually there will be galvalume on the siding. Here are 2 pic to view. The stone will be light brown with some bluish grey tones.

I'll try again!

Ok so white is galvalume, brown is rock, orange-ish is wood, and grayish-green is hardie? I think I would stick to using the wood only on the trim and beams, instead of on the side of the house. I actually really like the gray-green color you have in the pictures for the hardie. It adds some nice color.