1. Download a black & white img
2. Now select the poligonal lasso tool and select an area!
3. Now layer > new adjustment layer > hue/saturation, and use this settings
4. With the poligonal lasso tool select another area of the photo.
5. Apply hue, i use this settings: Select colorize, Hue: 30, Saturation: 25, Lightness: 0
6. Now add the final retouch
You should be finished! How do you like your image?
This is just a simple way of doing this. Remember I use Adobe CS3!