Rubio makes a product that give wood floors that grey look. Check them out online.

I was in favour of a colour similar to Jarrah but my daughter disagreed. My concern with black is that the decking is a shade of blue/grey and the house has much grey as well. I really like the black(ish) look but the pics shared show it on quite light surfaces i.e. cement or a very light wood colour. I actually have a full tin of blackbean wood stain. Do you know this colour?

red bricks with black and white looks very stylish so i would prefer gloss ironstone or white for the door with a brushed stainless steel handle

I'd be worried that red brick , presumably white door jambs , then a walnut or mahogony ( dark walnut ) look door will look cliched 70's . A cedar or even something like Jarrah will be different enough to the brick ( again , making the assumption you have crisp white or similar to break the tones ) to look the part IMO . Of course , the actual design of the door will have a slight bearing , but personally I can't think of too many options where I would prefer a walnut or mahogony tone , unless you were really embracing the era and have yellow dimpled glass inserts too haha .