PHRASAL VERB-ERG （使）头发长长以让原来的发式消失 If you grow out a hairstyle or let it grow out, you let your hair grow so that the style changes or so that you can cut off the part that you do not want. （使）头发长长以让原来的发式消失
I also let my hair go darker and grew out my fringe. [VERBPREP. noun (not pronoun)]
我还把头发颜色染深，并让刘海儿长长消失。
The red rinse had grown out completely. [VERBPREP.]