I do think a bright colour wouldn't look right with that architecture. I would be inclined to either go with white, or more likely a dark grey, maybe a bit darker than the roof/base of house.

Traditional style door. However bright red or lime green. White would be ok if you're a bit conservative.

If you want to play it safe then you could definitely go white. Being someone who loves pops of colour and something a bit different I would go for a bold bright colour like red.

Woodland grey (Dulux) to tie in with the grey exterior ..it's a lovely green/grey and I'd go traditional door

With the style of the house, I would leave the door as it is or paint it white. If you'd love a pop of colour, maybe you can put a couple of white chairs with bright-coloured cushions.

Or if you still want to paint the door, I would go with aqua or bright red as melf99 had suggested.

Definitely choose a door that references your façade! I would steer away from a contemporary design.
Before I give advice on the door colour, can you tell me what colours you have painted the house?
Is it Shale Grey Colorbond with Vivid White?

Thanks for all your comments. The colour of the weather boards is Dulux - Vanilla Quake, Dulux -Vivid White details and Colorbond - Wallaby for the roof, gutters and base boards

White or grey, assuming the roof colour is grey. Have a solid timber door and paint with a gloss paint for added effect.