The charring of wood as a method of preservation is nothing new and was known to European and Mediterranean builders as well as Asians. I have for years charred the bases of deck posts and such as a rot preventative. The practice is mentioned in John Fitchen's classic book Building Construction Before Mechanization. Some of the samples of this shown above are a bit crude. The most beautiful finishes of this type are rather labor intensive as some of the char can be brushed back off to some extent to reveal wood grain. The planter shown below has been coated on the interior with linseed oil, blackjack and turpentine and then set alight with a roofer's torch. The finish is cooked into the wood producing a carbonized insect and decay resistant surface. It gets filled with soil and so the char will be seen only at the edges.

The house is fairly small from the photo but elevated on a basement or garage plinth. If the base is brick, leave it as is. But whatever colour you chose, eliminate contrasts so if, say, a soft French grey, paint the walls, window and door joinery and roof flashing the same colour. A contract could be the new deck rail, but I would even consider painting it the same colour as the basement to link the 2 levels or just the same as the top. A bright glossy front door could break up the monotone.

We want something that blends in, but because it's a zinc and colourbond shed home, I want to choose a colour that makes it look more like a house and less like a shed. I was looking at basalt but my husband would prefer a lighter colour for keeping the place cool in summer. My original choice was windspray but I'm a bit concerned it won't contrast enough with the zinc roof...but perhaps better than dune that might look too 'sheddy'...so hard to decide!

Look at 'Iron Ash'. Its a treated version of what you're after. Don't know anything about it but seen it recently on the web. Overall avoid Merbau as mentioned above, as well as being an imported 'sustainably' managed timber.... Use local product's when available as they're manufacturered to high standard's, supporting local job's, companies must meet tight regulation's, etc. unlike other countries....