Things You'll Need
Instructions
Open your color image in Photoshop. Click the Magic Wand tool on your toolbar and select the entire area that you want to remain in color. You may add to your selected area by holding down "Shift" and clicking with the left mouse button, or remove parts from your selection by holding down "Alt" and clicking.
Click "Select in the menu at the top of the screen, then "Inverse" in the drop-down menu. This inverts your selection so that, rather than selecting everything you highlighted in the previous step, that is now the only part of the image that isn't selected.
Click "Create adjustment" (the circle that's half-shaded in) on the layers toolbar. Select "Hue/saturation" and change the value of saturation to -100. The color will vanish from everything in the picture apart from the area you initially selected.
Create the same effect using an alternate method: Remove all the color, then selectively add it back in. Open the file, select "Image" on the menu followed by "Adjustments" and "Desaturate" to make the image black and white, then use the history brush on the left-hand toolbar to paint the color back in.