He obviously dyed it to look cool/ probably differentiate himself from siwoon. I also just realized they are identical twins
he dyed it so he would look completely different from siwon because he thought that people would stop comparing the two that way.
Could be many reasons. He did it to fit in with a different crowd than his brother's. He did it to look different from his brother. Depending WHEN he did it, he did it to escape JooHoon so they think the dark-haired brother was him.
I want to know when he dyed his hair, before, around the time, or after the rape or suicide attempt.
My question is, why is Jiwook or whatever Siwon's brother's name is, look so different from the early chapters? His hair is like all blue and everything while Siwon's has stayed black all this time, did he like dye it? Or maybe it's just showing the accumulation of stress so his hair color it just gradually beginning to fade out from black to blue to eventually grey..... (︶︿︶)