Welcome to the TDH!
If you do a search, you'll find a ton of information on dyeing/painting the vest and cummerbund leather. I would start there before investing any more time or material on the project. It's worth the time to do the research!
In my opinion, it really isn't that hard to do ... it just takes lots of practice and the right tools. And LOTS of patience! You're opening up a can of worms here without realizing it! 
The right color? What is the right color? The colors from the official Zam pics and the "Dressing the Galaxy" book don't match up with the actual Zam costume we saw at the FIDM exibit or from pics we have from the MOM exhibit several years ago. You'll need to decide what the "real" color of Zam is!
Dye vs. Paint ... The vest and cummerbund may have been painted or dyed (the later is my own opinion). Either way, getting the color on evenly with an airbrush is a challenge to say the least. And this was done after construction of the vest, as the white front dart/seam shows.
Last year I dyed my cummerbund and it was difficult to get the color even...but then I hadn't given the lambskin the "Naptha" bath that MonCal had suggested in one of the threads. I'm going to be re-doing the cummerbund soon and will hopefully post the results.
Good luck and keep us posted on your progress!
