This is another take on how to colorize black and white photos by using a non-destructive adjustment layer to add color. This method lets you create a noticeably better image than just using a single raster layer.
PhotoshopBox.com says this method also lets you go back anytime and make changes to the image. The key is to use a Solid Color adjustment layer.
Hop on over to their site for the complete step-by-step tutorial.