Any suggestions for a new door color? ?

That would really depend on the color of the house

Sherwin Williams exterior paint in a Natural Style color. It's a lovely warm brown, not too dark, just right. Would look amazing with the green.

First check if there is a homeowners association as there may be rules about paint colors.

Depends on House color; are there shutters.

http://homeguides.sfgate.com/choose-color-exterior-door-30002.html

Black, dark gray or red...something to contrast the lighter color of the trim & siding.

Dark green, or warm brown.

A mid-tone green in the same color family. Take a photo of the house siding, check to see that it's true, then go to the paint store to compare paint chips to it. Keep in mind that it may appear slightly darker back in the porch inset. Sherwin Williams sales people have always been able to help me--friendly and knowledgeable.

Then buy a couple of large plastic inexpensive white flower pots, or clay pots, for either side of the garage door and paint the same to tie in the new color. Most pots can be painted, except for highly glazed ceramic pots. Again, sales people can help you select a primer for the pots you choose. Plant with yellow and white flowering plants with just a touch of deep blue like your accessory along the house front.

Red. Gray and red go quite well together.

Door should stand out. I think a warm red color would look inviting!

charcoal gray with a wreath the same colors as the siding

Aubergine!

I see a trend with gray (or grey) homes using a pop of color for the front door - teal being a popular choice. I think it looks great - so clean and classy.

I am envisioning chocolate brown! You could also add a crest or other decor above the windows on the left in the same color!

our realtor recently advised us to go with gray and white trim, then pick a color you like for the front door.