I have a serious case of house envy ...your home is stunning. I think I would look to the mortar or some of the subtle flecks in bluestone for guidance but look for something subtle and timeless given the style of extension. Also this is such a beautiful house I agree it's worth the small price of a colour consultant but make the decision slowly and paint up a large area to look at for a week or few before making a final decision.

Personally I'd use Manor Red. Probably won't see a lot of it anyway so if theres a discrepancy between Colorbond and tile it won't be as obvious. I'd also guess that the Manor Red would be a darker red than the terracotta tile? Could use Basalt for gutters and facias if you want a bit of grey perhaps?

The free-standing wood-burning stove is an option for repurposing the existing fireplace. Just be sure to have chimney swept prior to any flue installation. An installer will likely request this. It is for fire safety and it makes their job easier. Other option would be to have gas plumbed to the location and a gas insert fireplace. It really is a matter of preference. Obviously, burning wood is a bit messier and does, over time, leave a smoke residue on walls which just means more maintenance involved. As you mentioned a preference for lighter timber flooring, you could take a look at the various oaks available.

Interesting project there........when you're dealing with extending immediately from an existing building there are usually two ways to go....1. blend/extend seamlessly so that there is essentially no indication of any additions, or 2. separate/distinguish clearly between the old and the new. It's usually reflected somewhat in the floor plan as well. There is also a spectrum within both of those categories on how it can be done and whether its deemed to be done well or not so well. The issue I see with the facade articulation resolution (on your drawings) is that it is arguably neither one nor the other. The window/fenestration articulation is an issue because there's no confident consistency or sequence to the proportions of the new glazing areas. If you want "timeless" then you need to pull it into line with a particular style, either remain faithful to the reference/traditions/scaling/proportions of the original, or if that is either challenging or not providing the functional outcome sought, then consolidate the style/breakup of the extended windows to be visually contrasting yet balanced/controlled against the original. It's a similar story with the materials, it needs to all balance compositionally. Usually the decisions in this area come down to how best to balance also in conjunction with the roof form. And getting to the roof, this is again similar in that it's not ideal to mix & match gable and hip forms unless there's good reason to do so or you feature projecting gables out from a primary hip composition like as in cal bungs. I think you'll find it would be a better outcome to confidently work with one or the other here. In this case the existing primary reference is the gable form and this could be really be made the defining building form feature, but you need to decide upon how you articulate the gable forms - it's like there needs to be a clever/clear approach/language developed with some contemporary material to express the garage gable full height so it reads as the single material, rather than being broken up with the garage door and the gable infill - if it was a hidden door and the form finished more consistently the whole thing would look classier, professional and more elegant. There is super potential here to get this right and look amazing. I think the layout is all OK but some harder work is required/deserved on the facade, street presentation and form resolution, which obviously you are aware about since you've asked the question......possibly here, less in more ;) PD