Photoshop Tutorial: Desaturated A Photo and Color Only Specific Object by using Mask

Original photo

1. Open your photo.
2. Layer >> New Adjustment Layer >> Black & White
It will create a layer of your original image but in black and white color.
3. You may make your photo look darker to sharpen the color of your photo by move the scale shown at below to the left.

4. Since this is a mask layer, you may paint the layer by brush tool using black color to unmask, while white color to mask. Adjust your brush size accordingly to unmask your photo perfectly.

5. To make your original photo even more contrast, you may select your original photo layer. Image>>Adjustment>>Brightness/Contrast. Move the contrast scale to the right, to make it sharper and darker.

Here is it, the final photo.