Selective colorization

To selectively color an image that you have made b/w, do the following:

1) duplicate your color layer
2) Make the top layer active
3) Enhance > Convert to Black and White
4) Add layer mask [ 0 ] (button at bottom of layers palette)
5) Choose brush tool ( b )
6) Adjust the size and hardness in the options bar
7) When you have clicked the layer mask thumbnail in the layers, it will activate the mask and turn your colors b/w
8) Painting with black hides the layer, paiting with white shows the layer
9) Hit ( x ) to reverse your colors (hide/show)