Lavigne’s fans are going wild over her pink hair ... star Avril Lavigne pulled into the annual Rock Werchter music festival in Belgium this weekend and surprised fans by having her long locks ...

Gilbert Flores/Billboard via Getty Avril Lavigne has ... you haven't aged," she tells Lavigne. "I'm staring at you. And, like, I'm picturing you with your auburn hair. And I'm like, oh my God.