The modeling was done in P3D (from BBN) and I calculated the 3D data from bond lengths and angles in: "The Structures of the Pyrimidines and Purines. VII. The Crystal Structure of Caffeine." D. June Sutor. Acta Cryst. (1958). 11, 453-458.

Click on the small image to retrieve a larger one...

I also have a simple 2D picture which explains the coloring scheme, which may be non-standard (Intro Chem was a while ago :)