You can edit the image on different locations, I selected parts peace by peace, then edit the color, later I can edit the brightness and the darkness of the parts... I used the stardard options so it's indeed a little light right now... I can make it darker if you want...
But look for the program I just posted... it's useful for these kinda things !
I edit skins pixel by pixel only when I need to do eyes and detailed things, it takes awhile but the eyes are important to the model, so it's wurth my time.
Greetz,
Snake-D
P.s: You'll need to do some pratice runs... let me know if you want me to make an example with a darker part of the hair !