Highlighted hair can be dyed or color treated, but it should only be done by a professional hairstylist. Highlighting is an advanced styling procedure that involves certain types of hair dyes. Experts recommend caution when coloring over existing hair dye.
Adding another hair color on top of old coloring is a complicated technique that could easily go wrong when doing it at home. Choosing the wrong color might lead to an unnatural-looking result. In addition, putting harsh dyes on stressed locks runs the risk of damaging hair further. It is best to consult with a professional hairstylist, who does a thorough color match.