I don't think that really proves anything. As our daily diet shows, we eat a huge range of foods of all different colours than generally come out more or less the same colour i.e. brown.
I'm not discrediting the Liver Flush but those lumps are just faeces made up of oil... any kind of oil will come out in the same colour, just as eating different coloured solid food comes out brown. That's just what food/oil looks like after your body has processed it.
As a previous sufferer of Irritable Bowel Syndrome, I know that when my digestive system is out of kilter I get green coloured stools. This is because my diet wasn't balanced... the green stools from the flush are just a result of not eating any fibre or other substances, just the oil.
I believe the Liver Flushes cleanse the system, but the stuff that comes out aren't stones as people would like to believe them to be. This doesn't matter though, as long as it works for people, that's great!