Do you want to know how it's done? Learn how to use Photoshop the easy way!
If you are looking to create a colorized black and white photo from a color picture, please go to this tutorial.
This tutorial is about how to add color to a black and white photo that never was a color photo. Although you could use this same technique from a color photo that has been transformed into a black and white, the original thought is to add color to old, original black and white photos.
They used to do this in the "way back when", but they actually had to air brush in color. This is what they did to add color to a picture before color film was available. Fortunately with Photoshop this is a snap. This type of project is certainly easier to do if you have the use of a digital pen tablet. However, the mouse will get the job done as well.
This is the picture I will start with.
First of all we will create a new layer. From the file menu select Layer/New/Layer. We will name this layer "Skin Tone". Next from the layers palette drop down set the layer to "multiply".
Now you will want to choose a skin tone color. Double click on the foreground color tile and select your color. For this picture I have chosen the color E3D1C4.
Next you will want to select the brush tool. I chose a softround brush to use for this project. Right click on the canvas to change the size of the brush. Also use the zoom to get into finer detail.
Begin painting on the skin of your subject.
After putting all the skin tones in, I ended up with this. I adjusted the opacity a bit. You can get there from the file menu, Layer/Layer Style/Blending Options. Ahh, coming along nicely!
Now we will add another layer and set the layer property to multiply as before. Name this layer "Lady Hair". Double click on the foreground tile again and select the color for her hair. I have chosen the color 7F830E. As above, paint in the color. Create another layer (set to multiply) and name it "Man Hair" and paint once again. Change the color as needed. Keep adding layers for each item that you want to colorize. Doing this allows you the control to manipulate each item individually without affecting other areas of the picture. Here is what I ended up with.
Here is the before and after comparison.