I had a project at school that required me to do this. Here are the websites that I bookmarked for help.
http://www.metacafe.com/watch/421008...hite_to_color/
http://www.absolutecross.com/tutoria...os/colorizing/
http://www.swedesignz.com/photoshop/Image_Coloring
http://www.planetphotoshop.com/color...ite-photo.html
http://digital-photography-school.co...-cs2-tutorial/
http://www.devlobby.com/showthread.php?p=599
The last link is a program that auto colours I think. I never tried it out as I had to use the other ways for the assignment.
Edit: I just re-read the post and it seems you want something a bit different. My assignment was to fully colourize a black and white photo. I'll leave the links up anyway.