In Photoshop CS6, the new version of Photoshop, you can use special cropping tool and you are done, but that doesn't mean you cannot achieve the same result with older versions.
There are many different techniques and ways of creating a selective color images in Photoshop, let me show you the one where we use the black & white adjustment layer.
Pretty cool Photoshop tutorial, where we will add two text layers, one will be placed behind and the main at front. And I think you might really enjoy the final result, go for it and have fun!