I like existing brick but not that shade of green so I'd clad new extension in complementary colour to brick walls that aren't to be extended and I like white windows if roof doesn't need tiles replaced repointing etc I'd leave You could do basalt colour gutters etc and cladding with white trim on gables and depending on views light have some more modern perhaps double glazed windows on extension. Windows need to be all same colour on the front wall eg white painted timber if that's what your existing colonial windows are but don't need to be same shape. Just some ideas

it's possible to have a tiled or steel roof painted and the product, if applied well, should last for many years and can be reapplied if necessary..like any painted surface...not aware of any other product except these roof paints but, if your roof is already 30 years old it's probably time to have it checked for any potential weaknesses ...what is the roof made out of?

my suggestions includes cleaning all the brick walls and paving and repair any damaged pointing and grout, extending the roof sideways over a new garage without the Dutch gable, clean and paint the roof tiles in a mid colour or consider replacing tiles with Colorbond Steel for a more long lasting fix and opportunity to upgrade roof insulation, replace gutters in a dark colour and downpipes to match the brick colour, replace the steel fence with simple horizontal rails (and/or raise a solid brick fence to maximum height and render in the darkest fence colour) add Plantation shutters or venetians to allow light inside while retaining privacy and use Kate's idea of the pergola across the rear, add generous outdoor furniture to make an outdoor entertaining area, paint the garden retaining walls and fences in a darker version of the new gutter colour and fill the garden beds with shrubs to block out fences and neighbouring houses, keep the big palms and add some big shrubs and more palms to the front yard and paint the front door in the darkest version of the new gutter colour and what are the flat panels on the outside rear wall??

I'll be the opposite -- DON'T do the gutters to match the roof . Apart from the brown , every tone is quite light . As you say , the rear view , with the darker windows and fence etc looks great , but it looks and feels more modern than the front , and I personally wouldn't go too dark on the front profile . I'd do all the trim in a stark white ( the front gable , the top 40cm of the pillars , the garage surround , the windows ) BUT then I'd do the top board on the gable , and the top 'ring' on the pillars , and the garage door and the front door , in a mid red or burgundy . Possibly , I'd do the gutters in that too , and even possibly the beams up the gable , but I'd do the rest first , leave it a few weeks , and think about it . Too much red and white may be too 'Christmas' haha , but the yellowy beige is so dated , whilst I feel too much shale grey or any grey would also be self-defeating . Sharpen the look and attract attention .