Most Helpful Guy
I can give you serious and honest advise I hope as I have experience of this very situation.
First off it is important to say that if you love each other then it is vital part of that love should be to love each other no matter what color your hair is as well as wanting to please each other.
If your fiance prefers you brunette and he is the love of your life then you have no real need to do your hair to please others especially other men who may like your hair blond. After all if we did things just t opelase oursleves it would makea very selfish world. In this case I would have your hair brunette for your future husband and because you pleased him you should be pleased in yourself. You could maybe ask him to have his hair in a style you like or compromise and have your hair dark ask blonde/light brown.
I'm interested what your natural hair color is by the way. If it is naturally brunette then maybe your fiance does like you to be as natural as possible and that is a beautiful thing.
I used to have long hair and I have cut it short to show my fiance I love her and trust her opinions etc. I have not cut it as short as she first wanted but went shorter than I really wanted. She was touched I trusted her and wanted to look good for her alone. She told me she loves me no matter what hair (and its true) but that I would look better with it short...i love to please her and I actually really like my hair now, others have said the same so it was a worthy sacrifice and that's what love is...sacrificing your own desires for the sake of others, namely our loved ones.
God Bless hope this helps.