Rainbow hair won't last forever. The one major downside to bright colors? They are fleeting, so try not to get too attached.
Since the pigment sits on your hair's surface, expect funky colors to last about a month, tops. “Certain colors will fade out quicker than others—blues will go fairly quickly, yellow longer and then reds will stay for a while,” says celebrity hairstylist and NatureLab Tokyo ambassador, . “These rainbow styles often fade really nicely into pastel colors so touch ups depend on the vibrance you want.
Frequency of touch ups also can depend on how open you are washing your hair. If you are looking for really strong vibrant rainbow colors, I would say touch ups every 1-2 months.”Prepare to bleach.Read more on glamour.com