Gal will go grey (mid to dark grey) over 12 - 18 months. Initially VERY bright. The energy absorbed changes accordingly, from sub 5% absorbed to ~35%. Zinc maintains brightness for longer, though still suffers some dulling. Say 5% to 15% over time. This can be avoided by coating with a product called 'Sharkhide' metal protectant, used to stop aluminium boats oxidising. For there reasons many councils will not allow zinc or gal roofing (visual amenity, reflection issues), while making the houses more prone to requiring summer aircon at the same time. Surfmist Colorbond starts around 9% absorbed. If purely for energy reasons, a light colour might be the only option. If going dark, I would suggest at least doing the 'less aesthetically important' sides and rear in a light colour. Your call. If you go all dark, ensure you have good roof space ventilation for the summer that can be closed in the winter, and lots of well installed ceiling level insulation. Spray foam is more reliable over time than batts, see Spray It Solutions or similar (they have the Formaldahyde free Canadian Icenene foam).

I had a colour consultant come out and help. Taking into account leafy surrounds and colour of homes next door, this was the outcome - it came together really well: All exterior walls - Resene Double Truffle Roof, Gutters / Gargae door - Colorbond Wallaby Front door - Resene Ironsand Window & Frames - Colorbond Surfmist Fascia - Colorbond Surfmist We have a lot of red soil where we live so couldn't possibly go with a white exterior or I'd be forever cleaning the stain off lower walls. Good luck with it!

Just as a tip, those dark colours in your light brick arent' grey, they are a deep purple/brown also known as Burnt Umber. The midtone colour in that brick is also a purple brown in a natural mineral, in artists land that colour is called Indian Red, other similar hues are perylene maroon and piemontite. I'm an artist so very used to seeing different colours and their undertones. Colours that will go with that will be blacks that are actually red or purple based. So NOT monument which is a blue based charcoal. Blacks come in many different tones and it's important to match the undertone to your brick for colour harmony. Blacks which are complementary or blue based will stand out more but may not go as well. Which is why the grey blind seems uninspiring, it's a blue based grey. I'll name some colours in the Taubmans brand. I didn't pick Dulux because it has an abyssmal colour selection atm. Phantom Myst and Fable would both be good blacks to use on your home. Ruby Rose and Redwood and Russet stone would all go with the brick colours. Unless you train your eye to see hues and undertones it's very difficult to spot them which is why a colour consultants have a job. If you're interested learning colour mixing is fascinating there are even hues like red-blues which sounds paradoxical but ultramarine is actually a red based blue' A hack for creating colour palettes super easy. If you have Photoshop you can show it a photo and it will automatically create a perfectly co-ordinated colour palette for you of 6 or so colours which are exact matches to the colours in the photos. Any photo at all, and it will spit out pantone colour codes for you that you can take to paint shop and have them mix up. It picks up some dark, mid and light tones and you can have it create monochromatic, complementary, split coplementary etc palettes that work beautifully.

Being dark its going to be warm/hot , even with bush surrounds . What is your climate like ? I'm not a fan of all-dark , and in fact if you look at Julies inspo pics the first thing I notice ( not sure about you ) is the polished concrete , the timber deck , the lights , etc . Yes , I realise you go dark so it theoretically blends in , but even looking at your designers pic of your place , I notice the bricks and the timber window surround first , then the 'army green' , which is a sort of nothing colour IMO , and then the monument gutters , which , again just my opinion , doesn't do anything -- on a scale of complementing at one end , and clashing at the other , these are closer to clashing with the green IMO . IF you really insist on going dark and going with that green , I'd go a dark green for the gutters in preference to the charcoal , but even thats not ideal . I actually think an off-white rendered wall on the main wall to the left of your entrance door ( where the 'natural' wooden window box is ) would actually make the house , make it noticable in a good way against but also amongst your greenery , and the monument window frames and gutters will look even better , and it may even add interest to the khaki green to the right of the doorway .