women in blue

@Bleak GardeN: Thanks for your words, Bleak Garden.
It´s very easy. I work with photoshop CS3.
When you have open a photo in photoshop (colour photo), you must to choose "duplicate layer" (in Layer column). In the new layer duplicated you choose "black and white" (In image column). When you have the photo in black an white, you only must to erase the part of the photo you want in colour ( with "eraser" tool in tool column) . GOOD LUCK