Or, if I can be blunt- the difference between the american idea of being edgy and contercultural and the chinese idea of being edgey and countercultural is that the government in america will not run you over with tanks if you organize a public sit down. (However, make no mistake, the government in america will eliminate dissidents of enough threat in similar ways to china- see chelsea manning or the black panther movement.)

Of course it affects behavior in public, as well as clothing and dress. You can't openly support movements- including the wearing of logos, brans, slogans, sayings, etc.

"do Chinese millennials use hair colors that don't occur in nature as often"

I'm pretty sure dyed hair is still considered popular and fashionable in east asian cultures, given the pop bands coming out of there!