I looked up some rainbow hair, and it's like SM's tradition.
They did Sulli.
Also Haechan.
And Hyoyeon too.
+ Key also did it.
Netizens comments :
(+85,-3) Legendary white hair.
(+75,-28) For me V's blue hair. I really like it.
(+70,-2) The rainbow hair legend.
(+33,-3) Kim Junmyeon blonde hair.
(+19,0) The hair of the sky.
(+18,0)
(+14,-2) cotton candy jiyong
(+13,-4) Kim Seokjin purple hair ㅠㅠ
(+13,-1) Vernon silver hair.