I have always loved gray siding with the black shutters and a red door.

I too like grey with black, but if you are looking for a change, depending on the shade of grey you have, hunter green can be really nice along with some white trim.

Before we put vinyl siding up, our home was painted gray cedar, white gutters, etc. gray>black roof. We had deep burgundy shutters and front door. A deep 'colonial blue' also would have worked (the gray had a bit of blue tone to it) as would a cool hunter green.

Here's a little tool you can play with. Go to Owen's Corning siding. On the far left under "Tools and Resources" click on "Exterior FX Visualization Software" in the drop down menu. At the next screen click "Start Designing". You'll then be asked for a zip code (put in anything, doesn't have to be yours ;) You'll then be directed to a screen with sample homes to choose from. Pick one of those, similar in style to yours if possible.
Next screen will show the house you've chosen with coordinating "Palettes" on the left. If you click one of those you'll see it on your sample house. However, if you look up at the upper left, there is a second tab you can choose: "Custom Design". That's where the fun starts ;) You can "Select a Surface" and choose the roof, siding, add stone or paint. Select a roof in similar style color to yours, then siding. Once you've done that under "Select a Surface" choose "Paint". Then you'll get a drop down menu to paint doors, windows, trim or the whole house if you like. You can play around with different color combinations and see which ones you like ;)

I also love gray siding with black shutters with almost any color door. However, my girlfriend has a gray house with darker gray shutters and a mauve door. It is beautiful very cottage like. Paddytc