You need to have Shampoodles open for two weeks before you get the option for contacts. I'm not 100% sure if you need to get at least 1 haircut there before she gives you the option but I would just to be safe (if u haven't already). If it's already been more than fourteen days and you've got a haircut there and you still can't change your eye color I'm not sure what the issue is!
Ahh I can't remember :[ I have different characters and they have the contacts unlocked but I really can't recall if they had to each wait 14 days too. Probably should try giving them a haircut too to be safe lol