Only people who are truly beautiful look good with black hair
Black hair only looks good on really pretty people
Only really people can pull off black hair
Only people who are truly beautiful look good with black hair=本当に美人な人しか黒髪は似合わない
truly=誠に
veryより強い言葉です。
Black hair only looks good on really pretty people=黒髪は本当にきれいな人にしか似合わない
Only really people can pull off black hair=本当に奇麗じゃないと黒髪は違和感がある
pull off〜=〜をしててもおかしく思われない、〜が上手い・馴染む
I don't think I can pull off that mini skirt=私にはあのミニスカート似合わないよ
Not many people can pull off a lie like that=そんな嘘を付いてバレない人なんて中々居ないよ