We used spotted gum for our decking and love it! We got it for $4.25 linear metre from Masters (any lengths that were inferior they were happy to replace). Our deck was built next to our near-white pavers so merbau was out of the question due to its leaching (plus we also were wanting an eco-friendly local hardwood if possible).

A house in our street is very similar to this, the owners have done a fabulous job celebrating the style of the house, the roof line and bessa blocks have been made a feature, they have decked the front and landscaped the gardens, it is dressed beautifully with 59/60s style pots lowish profile with three legs accopulco chairs out on the deck. I wish I could take a photo (but a bit creepy - going up and taking photos of some one else's front). They have put in new windows and doors. The front garden is large and they have views over the inlet here. It has gone from one of the worst houses to something pretty remarkable. The new Windows are black framed

Grey and cream go nicely together so maybe go softer paler shade of house “yellow” (ie warm white perhaps natural white) and perhaps basalt as think gutters are deep ocean and basalt more neutral Grey or ask body corporate what colours are and google matching colours

I agree that it can be upsetting at this stage but your timber will all darken naturally and the difference will become less obvious over time and once you have furniture and rugs in place it's likely to be one of those issues that only you and no one else will notice. And I defy anyone to not have something like this in their house which has been newly built/renovated. I know this isn't terribly helpful but I don't think ripping anything up to start again or going to great lengths to seek recompense from supplier/installer is going to help your blood pressure either (by all means raise concerns with them and ask for suggestions from them).