Kristin Ess The One Purple Shampoo 296ml is great for toning blondes and brunettes and is also sulphate-free, which can be a hard combo to find. If you like ashy or pastel lavender tones, you can use this every time you shampoo. If you like neutral tones, use it only when needed to cut brass. Use this with or without the one purple conditioner on natural or color-treated hair.