I just think it needs more bright white trim around the windows and the fence painted also white. Going round to the back addition, I would paint the timber boards the color of the stucco, trim white and get some great deck furniture and lighting.

A green roof pairs well with gray and white homes. For a subtler look, pair a green roof with a siding in a lighter shade of green. I think you are on the right track .You have chosen harmonious shades . New paint doesn't have to match existing colors, but it should harmonize. Some general tips are- Green roof - Gray, green, or white house colors. You could use a dash of yellow also.

To answer your question I would paint the body of the house blue, all trim white, and then the "fringe" which I think ties into your porch decking, I would paint it the gray. It is a good "grounding" color for your home. Sherwin Williams has a cool web tool. Take a pic of your house and load it onto their site. You can "color" away on your house. When I painted my house for the first time, I did not want the garage door to stick out, wanted it to blend into the house. Everyone said it would look weird, needed to be painted the same as the trim. Used the Sherwin Williams site and realized want I visioned looked good. I have neighbors of dubious design skills! Ha! Ha!

I don't know how hot it gets in Auckland in summer (I've only ever been to NZ in winter!) but if it gets hot, then go for a pale colour. Dark roofs should be kept for cold places!