Adding color to a grayscale image is a neat little effect you see all over the place. The process of colorizing a grayscale photo certainly seems straight forward enough, in that it probably involves grabbing a paint brush and painting color onto the image itself. The problem, though, is that while you would succeed in adding color to the photo, you would systematically destroy any detail it once contained.
This tutorial shows how to use smart brushes to make a true layer mask and Photoshop channel feature to make a black and white with selected parts in color. Also, learn how to make a slideshow in Elements to magically reveal colors within your photo.