I agree with Billmore Homes paperbark is a very nice colour and goes well with Jasper http://colorbond.com/colour?Category=4969402186C2455AB302B1ECD6FE7176 The idea to use double strength is good for outside projects because the light can affect colour so much at different times of the day. Soft greys are back in fashion too so don't overlook Ironstone, Basalt and Wallaby( the web link shows what I mean by those colour titles) if you are stuck with the blue door it can be hard to coordinate with blue but you can alter its shade slightly by a freshen-up coat of the original colour or a tone or two darker or a few drops of black (and I mean drops) is amazing the depth it adds to a paint tone without changing the overall colour.

Fashions comes and go like the pants from 70's but with black windows I would go light colour, dark is nice but little depressing. Drive around new suburbs and see witch one makes you happy when you see it, then that's the one for you.

Colorbond steel is usually powder coated in manufacturer and we've had guttering up to 8 m long powder coated off site and had no problems with chipping although you should ask the roller door makers to custom colour.

I don’t have any practical advice but love the look. If you google images for Porters Paints Palm Beach Black you’ll see some great exterior inspiration.