I don’t want sex????

Lately I have not felt sexual towards my long term boyfriend. I have no interest in having sex with him. A big part of it is because he dyed his hair blond. I think?? Since then I haven’t been attracted towards him. I love him with his black hair and beard. But since he died his hair blond, I have no sexual attraction towards him. Am I wrong for this? I feel bad. I love him as he is. I literally have to think about what he used to look like, in order to enjoy the sex. I’m a terrible girlfriend.