This thread is awesome. I've been making coffee soap in PVC molds for years now. It will be darker if it gels, but I've never made any quite as dark as CursiveArts' soap. I make 2 versions; one is my usual olive/palm/coconut/castor w/5% SF and 33% Coffee (instead of water); the other is exactly the same, except I rebatch with some confetti'd soap and add ground cinnamon and coffee grinds. The plain version is my slowest seller, but the goofy rebatched one is one of my most popular offerings.
The discoloration noted up-thread happened to me BITD, when I used spent coffee grinds, straight from the brewer. B/c the coffee grinds were still wet, they leached out some water which would discolor the soap; in one case, the bars started weeping from the excess liquid coffee present in the grinds. I toss in unused, dry coffee grounds, now. To cut costs and ensure some truly dank, stank, and strong stuff, I've been using Cafe Bustelo or Cafe Supremo (super-cheap, super-dark coffee available in the "Latin" section of most grocery stores.) Because I am a coffee snob/ pt barista, some folks do get upset by this. The way I look at it, it isn't worth it to toss some high-buck FTO/organic stuff into a soap recipe. Hence, the Cafe Bustelo. (Which does, indeed, hold more aroma.)
Keep this thread going a while; i'll try to find the time/energy to post some pics.