i always feel like when idol rock different hair color their skin color looks different

Some idols look fantastic in with pink hair imo. Especially Sana, Seokjin, Sulli, Gahyeon, Moonbin, chanhee, jimin, taeyong, Jaemin and more.

They totally look like an anime character.

bc thats how color contrast work!

Thats like the first lesson in painting

Take the same pigment, put it on white paper then on black paper and they will appear different to your eyes

that's how colors work but the makeup artist also changes a lot of things to keep up with with hair color