BM Nantucket Gray definitely looks green to me, so if you don't like green that probably won't work for you. I love the color though (so much that we're painting our house Nantucket Gray this spring!), and think it looks very "Cape Cod" :) I'm from the east coast and still miss it ^_^

Can we see your house from the front, too? I like this color combination (but my thoughts might change if I can see other angles).

Paint the metal around the posts yes they will be wood underneath but not pretty. I would start with better landscaping if you plant in front of the foundation you will ne need to paint it. Google foundation plantings and you will get all sorts of ideas the same on the right those little shaped bushes need to go add some color . As for the shutters I would paint them , the front door maybe a nice blue Use a metal railing the same color as the posts

Are the hexagonal windows for light or just air flow? I feel like updating them to something rectangular would be a greater return on investment than painting such nice neutral brick! I’d also look at ways to make the entrance more special, more substantial railings, instead of two small light fixtures one bigger fixture, move the address number somewhere more visible. I think the flower boxes are quaint, but I’d get bigger shutters, ideally shutters should be the size of half the window and your house facade totally allows for proper sized ones!