I agree with Susie. My experience is it doesn't last long term. Also, its expensive. Adds to the cost quite a bit. I do exactly as suggested and don't scent a portion of my soap and color that. However, if your FO causes a really dark brown, sometimes it can overtake you colored portion some
You can easily work with dark coloring fo's by separating out batter and adding various amounts of fo the separated batters, leaving one unscented. It can actually make a pretty soap. You can also use some bright yellows, greens and pinks in a portion of the batter and they will stand out against the brown. Neons work great also for adding a bright swirl in dark brown
I've had really good experiences with the one that I buy from Bittercreek North. Granted, I've only ever used it with 2 different FOs so far that only discolor to a medium tan/light brown color (Santa's Pipe from Sweet Cakes and Sugared Spruce from WSP), but my batches that I've made with the stabilizer (which I colored white with TD) have remained a stark white color for at least a year, which works out great if you know your soap will get used up within a year.
I use an equal amount of the stabilizer as per the weight of my FO, and I add the stabilizer in with my fats/oils (instead of mixing it with the FO first). I mention that, because that was the advice given to me from other soapers who had experience working with it. They said I would get the best results mixing it into the batch that way, and so far, their advice has worked out very well for me. One of these days I need to try it out on one of my FOs that goes really dark brown, and see how it fares.