I dye my hair all the time and my first boyfriend hated it but I loved it. He insisted I stop dying and let it go back to my natural blonde, which I hated. He got mad, and threatened to break up with me, so I bought hair dye remover and stripped it back to my natural colour, thinking he'd agree that it didn't suit me. I hated how it looked but he told me he loved it so I didn't dye it again. Then a week later he told me my shoes were ugly and took me out and bought me a pair of heels that made my feet hurt and made it impossible to run in but he told me it looked sexy so I threw out my trainers. Then another week passed and I wore a baggy hoodie and loose jeans and he told me he didn't like the outfit I was wearing and dug around my wardrobe and pulled out a bodycon dress I'd bought for my cousin's party and chickened out of wearing and over the next few weeks he took me shopping and picked out more bodycon dresses and miniskirts and low cut tops and I was beyond uncomfortable but he told me he loved it so I kept dressing like that. Within a few months I didn't recognise myself.
It might not seem like a significant change right now but trust me when I say it snowballs and before too long it becomes significant. Maybe he's not as bad as my ex, but please listen when I say that if you want to stop dying your hair, then stop, but don't stop just because he wants you to.