That's a great question.
Basically what I did was go through the text and make changes where things had evolved in digital photography. Items such as acknowledging the new 4:3 format by Olympus, the Foveon sensor, and stuff like that.
I also added some new discussions based on topics that have been popular in my workshops, such as Jpeg vs, RAW.
As for the pictures, not only are they in color, but I actually went out and reshot over half of them, often with the same models. I think the current batch illustrates the techniques better than in the first edition. Second edition is also easier to read because of the redesign.
All of that being said, the first edition is still quite current and useful. I'm sure the sales dept won't appreciate me saying this, but if your original book is still in good shape, then so are you.