Is there a certain program that you used to do that with the door? I have been wanting to do that forever and can't find a good program to do it with. Nice picture!
You can do it with almost any program, including MS Paint - just select the door, copy it, make the whole picture b/w, and paste the door. Of course, certain programs (like Adobe Photoshop) will do a much cleaner job, and will allow you to make a more specific selection, but that would work.
Otherwise, you can color over the black & white door in Photoshop on a semi-transparent layer. That will keep the shading and add color over it.
