Schwarzkopf Bonacure Colour Freeze Silver Shampoo. Pigmented micellar shampoo for cool colour tones. BC pH 4.5 Color Freeze – for coloured and highlighted hair. pH 4.5 is known in skincare for balancing the pH level of the skin to maintain a healthy condition. In haircare, it’s used to freeze colour pigments inside the hair matrix, promoting long-lasting colour vibrancy.