With the color palette outside your home, you have kind of a blank canvas, which is an exciting opportunity; but, it can also make it hard to decide. To make it less daunting, try looking at other factors for inspiration.
Try using an accent color from inside your home to make the door part of a cohesive look, or use a color that compliments other elements outside like brickwork or flowers in your yard, or something that coordinates with the surrounding houses.
Finally, you can choose a color by the meaning it conveys like red (strength), yellow (joy), or blue (peace). Whatever method you use, pick a color that you like and you will always be happy with it.
I vote for yellow. It doesn't have to be school bus yellow. A deep buttercream yellow would look nice.