Color of stones, sludge

As I mentioned in my previous post "My experience" I have completed 3 flushes. In all of those flushes I have never seen dark or green stones or sludge. Everything that I've expelled including lots of sludge and some large stones have been orangey-yellow. I am curious about this. If there is info about this I have missed let me know. Or comments? Thanks! I appreciate all the support here.