If you are sure you still have the original top then it is Black Denim (15). The Black Diamond (35) color wasn't used until '03. One thing to keep in mind is if you plan to replace your top in the near future, I'm pretty sure Bestop only makes sailcloth replace-a-tops in Black Diamond, so your doors might not match then.
Also, either way your top has been fading for 7 years, so either will look darker out of the box.
Edit: Not sure of the color difference when both are new, but I bought those doors and a new top in Black Diamond to replace the denim I had. Texture is different (diamond is smoother).