I have used green tea in soap before. (Using the liquid for water, and tossing in some tea leaves) It faded pretty quick, but the tea leaves provided a nice texture. They turned a blackish brown and stayed that way in the soap. A lot of times the natural "dyes" tend to fade, but I am trying to switch over so I'll share my results with tesing going forward... Hopefully someone else will chime in with more experience with what you are asking about.