I played around the famous layer mask of Adobe Photoshop to achieve this picture.

The process was quite simple:

• I duplicated the layer of the image
• desaturated the upper layer
• created a layer mask for the upper layer
• clicked on the layer mask
• selected the area that I wanted to have coloured by the Magnetic Lasso Tool
• set the foreground color to black
• painted the selected area of the layer mask with the Bucket tool letting through the colors from the coloured layer