I used photoshop CS5 extended version (my first photoshop, and I believe that the steps are the same for previous versions).
I open the raw image in PS, then I duplicate a layer. Then I go to layer and make a new adjustment layer (black and white). Now your picture looks black and white, then you use the brush tool, then set the desired size for the brush tool, and start to bring the color back to where you want it. Before you do this, look at your vertical bar on the left side of your screen.... at the very bottom, you have an icon of a camera. Right above this you have an icon where there is a black square on top of a white square (it is called Set foreground color). You have to remember to have the black on top of the white, otherwise it will not work. However, If you overdo it, or paint back the original color where you do not want it after all, you switch the white to lay over the black, and then you paint the black-white back on it. just remember to switch back to have the black on top of the white again, then go back to brush tool and start extracting the color out again.
Good luck, and I hope this explanation was good enough, and I would love to see your results:)
Adding another picture here, where I used shallow depth of field, and then you can see how hard it becomes when the borders are not totally clear. I am also posting another picture where the same border becomes a problem because of long exposure creating motion blur.