I don’t think that most Poskim today say that. I have never heard of anyone saying such a thing.
And back in Europe where no one covered their hair they would have said the same thing, that they “never heard of it”.
Obviously you should ask your LOR, but before worrying about the nuances of which color nail polish (where you agree there is no Issur), you should certainly be Choshesh for a significant Shittas Rishonim and Achronim, who hold there is and Issur for non-braided hair.
Go ahead and ask your LOR. I’m interested in what he would say.