Since highlight is a chemical process that seems to move farther down the hair as the new growth emerges… the majority of people retouch their hairs every 6 to 8 weeks since the hair grows an average of half inch per month… so, at the end of the eighth week, we notice an average area of one inch at the scalp with the natural color while the other part of the hair still enjoys the highlighting product…therefore, in order to avoid the mixture appearance of colors (natural color+ highlighting color) we should try to touch our color every 6 to 8 weeks…