SYSTEM 4 - COLOURED HAIR - FOR PROGRESSIVE THINNING HAIR. Protect and refresh the scalp with Nioxin’s 3-part System 4 Scalp & Hair Treatment for Colored Hair with Progressed Thinning. This diameter-increasing leave-on hair and scalp treatment is particularly formulated for colored hair with progressed thinning. Nioxin’s treatment Scalp Access Delivery System 2.0 technology helps prevent hair loss due to breakage, providing a refreshed scalp environment. Nioxin’s Scalp and Hair Treatment is the final step of a 3-part System, designed to strengthen the hair and amplify hair structure.