This tutorial will show you how to use Photoshop to selectively reveal only the color you want in the areas you want in a photo.

Step 1: Open the image.
Step 2: Create an adjustment layer by selecting Layer > New Adjustment Layer > Hue/Saturation from the menu, and click OK. Saturation dialog box appears, lower the saturation to -100.
Step 3: Select the paint brush tool with black as the foreground color, and set the opacity to around 60%. Use a soft round brush.
Step 4:Paint over the areas where you want the color to show through. Then painted over other portions of the image with the opacity set to around 10% and an increased brush size to add a little bit more color.

That is all there is to it. If you make any mistakes, you can switch the foreground color to white, and paint over the mistakes on the adjustment layer to fix them.