I used Photoshop CS5 to create this & while I probably didn't do it the correct way, it worked & was fairly simple!! I'm going to attempt to try to explain it here but I'm not sure how that will go :)
open photoshop & select the photo you want to use (I suggest something fairly simple with easy to follow lines to start)
create a duplicate layer by right clicking on the image & selecting duplicate layer
make sure duplicate layer is selected then click on the create new fill or adjustment layer button (forth right from the bottom corner)
select black & white
then simply select the suitable size eraser tool & rub over the area you want the colour back in
then click layer, flatten image & save your work
