Taehyung seems to have pink hair and this is is what I got when i researched what the colour meant:
MK Ultra symbolism is used by handlers to advertise their slaves. Just like cat symbolism is used to showcase the subject's sex-kitten alter, the colour pink is used to display the child-like sexual alters. This type of symbolism would be used for a BETA slave or someone under sexual programming. BETA programming has the most primitive sexual instinct and no moral convictions.
"The colour pink is traditionally associated with femininity, sexuality and purity. It is also used to characterize a child-like personality, which is why in programming, it is almost always associated with child alters, which are related to the core personality of the victim. Programmers typically view this alter as weak because it is easy to break down and make cry. They can exploit it to their advantage by attacking the true-self of the victim. If the handler wants to advertise the virginity of the victim to other handlers, they may dress them in all white or pink, signalling that the child is still a virgin, which means a lot more money for the handler when the victim is sold into prostitution. As the victim grows older, it is less and less likely that they are still a virgin, which is why the colour pink is also used to symbolize sexuality."