when we first met and then got married, my husband didn't like the way i had my hair cut - a very short crop (i still have it this way 35 years later). i just used to smile and say well, it's my hair so i'll have it how i like. he would comment each time i got it cut, but i never changed it.
i suppose then, i think that if it's not a major thing, or something which has a huge impact on you, then it's all part and parcel of the person and you should let them do what makes them happy without trying to change them. if you can't ,then perhaps you have to ask yourself if you can put up with whatever it is, or walk away.