May I suggest a cap of your pavers on the wall and the a slightly darker gray that relates to the privacy fence beyond? That way horizontal surfaces and vertical surfaces show similarities and blends/blurs the separations?

As the appearance of the garden has a modernist style with the straight lines and concrete furniture how about a Mondrian influence and add a bold strip of blue? It is a pond and with the right shade it could look really relaxed and contemporary. My daughter's suggestion is a chalky lilac!

Thanks for all the great ideas everyone and sorry I didn't explain the polycarbonate a bit better :) This is along the lines of what we'll be using... http://www.psp.co.nz/building-brands/corrugated-sheeting/suntuf-polycarbonate The area is an absolute sun trap and we're hoping to use it as an extension to our living space, especially on rainy days! I've just sent my husband out to get a few pots of different stains for is to try - darkest brown (cedar) and a lighter brown (rustic oak) both by Cabots + the black we already have. Hopefully we can decide between one of those! I probably should have mentioned we will have black aluminium pool fencing running along the top of the second retaining wall - so the real question is do we keep everything black (pool fencing, horizontal fence, retaining walls and pergola) or do we go with a dark (or even light) brown for the pergola and retaining walls.... We just keep going around in circles at the moment. Decisions, decisions! Thanks again :)

Without knowing any more info , I'd say its near impossible for anyone but you to know what colour/s to choose -- do you want the house to blend in but have its own style , or do you want it to stand out ? What colours are your main furniture items and even kitchen etc ? For xxample , if keeping the beige walls , how about doing the eves and gutters and garage door in a tangy ( bright , but not glaring ) orange -- this would work with the existing colours and not require a complete repaint . BUT if your kitchen was mainly various shades of , say , green and teal , and your lounge suite and duvet covers were mainly blue hues , that may 'feel' funny , clashing with the exterior ? Of course , blue and beige exterior may not work with the brown aluminium , as youve recognised . Another option ( a bit hard to tell from the pictures ) is that a light grey ( repaint the beige ) with mid-charcoal base boards may work with the brown aluminium , then a bright colour on the gutters and front and rear doors to suit -- anything from sea blue to bright yellow , orange , red , even white or off-white would probably work .