That's easily achieved with layer masks.
Is there any chance you could go into a bit more detail? I can pick it up quickly, but I have not used masks yet in photoshop.
Currently I have 3 layers of hte same picture. (using the example above for ease) I have a layer with just the coach on it and background deleted, the original picture, and a duplicate of the original picture with the saturation taken completely out to make it black and white.
If you already isolated the coach, you don't even need masks.
- Make the desaturated layer your Background;
- make a new layer above that, and fill it with your blue (or any other color you want), Adjust the transparency of the layer to your taste;
- on top of that, place the coach on its own layer.
You don't need the original image.