I don't think hair dying is femme, per se. However, I do think it is more difficult to pass if you have certain bright, unnatural colours.
My hair is scarlet and has been so for years. And I have seen cisguys with the same hair colour. However, I have been experimenting with toning it down and, yes, a less in-your-face colour does definitely look more masculine. The cisguys with bright red hair look male in spite of theirs, not because of it.
Is this going to stop me having bright red hair. Nope. It's me. But, I am now down to dark red sides and a scarlet Tintin quiff. Compromise.