I never really noticed any real practical difference between purp's and other strains. Just bag appeal to have high potency, with a completely different color. Which is what helped the purple traits stay around, as we enjoy breeding things like that. However, in the last few decades, it's been crossed with SO many things in so many ways, most "purple" strains, even pure ones, don't always turn purple. So you may VERY WELL be buying some purps, even if it isn't the color purple. I've seen a dozen different levels and types of purple's on buds, it's a beautiful, but uncertain thing.
