A few days before you go to your hairdresses for your colouring session, we recommend that you clarify your hair. Use a mixture of shampoo and baking soda, clarifying shampoo by itself or even apple cider and vinegar. After your clarifying treatment, condition your hair as normal.
Deep conditioning is also vital for restoring moisture before your highlight treatment. This will help restore the pH of your hair, whilst also making sure that your ends are moisturised. All of this means that the colour and hair will mix evenly. Hair dye usually dries out hair, so by conditioning beforehand, you are bound to fight against the dull version of the colour you desire.