While some shampoos and conditioners offer ingredients to boost colour-treated hair, another important thing to consider is whether or not the products are colour-safe. Both the popular Olaplex No. 4 Bond Maintenance Shampoo ($14-$28) and No. 5 Bond Maintenance Conditioner ($14-$28) are exactly that. They work well for people who want to keep hair as strong, protected, and frizz-free as possible, while also safeguarding its colour.