To do this, you’ll need to first open your picture in PhotoShop. Choose the Magnetic Lasso Tool, and slowly but surely trace the outline of the portion of the picture that you want to have the color.
Once it’s selected, go to Edit>Copy to copy what you’ve done, and then de-select the flower. Make a new layer, and go to Edit>Paste. The new layer will only consist of whatever you just outlined. Go back to your background layer, and go to Layer>New Layer Adjustment>Black and White. If your colored portion isn’t aligned properly, you can easily drag and drop it into place.
That’s all there is to it. I know there are a lot of different ways of achieving this same effect, but this definitely seems to be the fastest – and easiest.
Thanks, Michael, for an excellent tutorial!