Okay, so here is my tutorial for how I do my colorizations. I use GIMP instead of Photoshop because I’m more comfortable with it. (and its free!) The steps should be close to the same if you are using photoshop.

Step 1:

Start by opening all the photos you’ll be taking colors from. For skin, eyes, hair, mouth, etc. And open the one you’ll be coloring. In order to colorize a picture it has to be in RGB mode and not grayscale (all of terry’s are in gray scale so you’ll have to change that. Do that by clicking, Image>Mode>RBG)

Step 2:

Use the free select tool (lasso icon) and go around each area of skin to select it. Be sure to only get skin you want colored. Anything like shirts, bracelets, etc shouldn’t be in the area because they will be colored also. You may have to do each area of skin separately for this.

(Notice I’ve only selected one arm so that I don’t get his shirt in the colorization area.)
 Then Bring up the picture you are taking the skin tone from and select an area of it.

Step 3:

Now, click back on the photo you are coloring. Then go to Colors>Map>Sample Colorize.
 

A new window will pop up. And in the drop down menu on the right, you click on the picture that you selected the skin on. Then click Get Sample Colors and then click on apply. Then Close.

Step 4:

Now, If that shade isn’t exactly what you want, you can adjust it by using Hue-Saturation in the colors menu, or I prefer to use Curves. Click on Colors>Curves to open the window and then drag the dots on top and bottom either left or right until you get the color you want. Now ITS important to click the + sign to add this preset before closing the window. that way you can use that same shade for the rest of the skin. Do that and name it something like skin. Now click okay and close the window.

Step 5:

Now, repeat steps 2-4 for the rest of the skin. For the face, its fine to select the whole thing without worrying about the eyes and mouth, we’ll be changing those later.

Step 6:

Now, we’re going to do basically the same thing for his hair. (and the rest of the picture too. Select the entire area of hair  for the picture you are coloring.

(Selecting the hair doesn’t have to be perfect, it’s going to be dark enough to hide that. Now, bring up the photo you are sampling the hair color from and select a portion of it .It doesn’t need to be all of it, just some. )

Then repeat step 3 and 4 as well.

Step 7:

Now, we’re going to work on his facial features. We’ll start with the eyes. First, we’re going to lighten the whites since the took on the color of  the skin. To do this we will use the Dodge/Burn selection.

I prefer to move the Exposure to about 30 percent so it doesn’t get too white to quickly. Make sure Dodge is selected as thats the light setting and Burn is to darken. Select a size of cirle that isn’t too big or too small and just go over the white once or twice until it looks a good shade.

Do this for both eyes

Step 8:

Now we’re going to color the iris’ You can either use the Ellipse Select Tool or the Free select tool(Lasso) But select just the circle where the color is going.

Now, bring up the picture you are using for the eye and select that color region and repeat step 3. Do this for both eyes and you should end up with something like this:

Step 9:

Select the lip area with your free select tool. Now, lips are a bit trickier, as the color doesn’t always work, so try out a few options, use the curves tool for shades until you find the one you want.

Step 10:
Use the Dodge/Burn tool again to lighten and darken some areas. I use the Burn setting to darken the hair line so that it blends a bit better. And for the beard to darken that as well. Sometimes I use a little bit of a Blur (that’s the waterdrop tool) around the edge of the lips on about 30% exposure just to soften that line.

Step 11:
Finally use the curves, hue-saturation, or brightness contrast to adjust the colors in your picture (without anything selected) add your tag and you are done!