A lot of fans were shocked when they saw Thunder's new pink hair for 'Smoky Girl', but he apparently did it to keep a promise to his fans.

He was a guest on SBS Power FM's 'CulTwo Show', and he was asked about his new hair color. He revealed, "I actually did this as a promise to fans. When I saw miss A' Jia's hair [for 'Bad Girl Good Girl'], I promised I'd have the same hair to my fans. I was finally able to keep my promise after 3 years."

Looks like Thunder really takes his promises seriously! What do you think of his pink hair?