If you want the new garage to look like it's meant to be there, IMO the only way to do that is to have it faced with brick that matches the house's, shingle it with the same material, and match the gutter style and color (or "colour," if you prefer :).

Anything else will make the garage an obvious afterthought.

Or are you looking for contrast with the house?

As for the door colors, I think what you have now for the front door works pretty well with the house. However, I think that a dark-colored garage door might be a bit overwhelming. I'm not a decorator, though.

Speaking of such matters, have you considered hiring a decorator to help with this?

Are you replacing your existing roof or just adding on the garage and extending the current roof over the garage. Will the garage be attached to the house?

I like your brick and your roof color. The front door should be a different color to draw attention to the front door and away from your future garage door. A wood or wood look garage door would look wonderful on your brick home. If you need to go with a different material, then a color that blends with your siding/brick would be best IMO. If you go with high contrast color for your garage door it draws all the attention to your garage rather than your lovely home.

Looking at colors that work for your front door, try one of the accent colors below. I think the goldenrod or basil or meadow would look terrific on your front door. JMO

Thank you for the suggestions! The garage will be a detached garage. Not connected to the house at all, just beside it. We weren’t sure if our house exterior colours looked outdated. Therefore we would change them if they do look outdated (the roof and gutter/soffit colours) and match them to the new garage.

I agree your brick is classic and to match the garage rather than contrast with it.

Don't change your gutter or roof colors as both work well with the brick.

if you want to amp up the front a little bit the change in front door color to an accent color and landscaping will be all you need.