Yup I agree with Paulette that the color of the grapefruit has absolutly nothing to do with the success or failure of a flush.
More specifically since the grapefruit is mostly used to mask the taste. I have used red, pink and the reg'ler yellow GF and while I prefer red for the taste. They have all been succesfull flushes.
I think a big contributor to the success of my flushes is that either from the day before or at least the day of the flush I eat no solid food and only veggie juices. This just simply makes sense to me and when folks ask me about the Liver Flushes I really recomend that at least the day of the flush not to have any solid food their systems. Also I eat very well the whole week of prior to the flush I . Mostly raw and juices.