He is buying them for you so he should have a say in the gift he is giving:
If it's more important for him to be giving the gift he likes than it is for you to receive a gift you like then his motivations are skewed. It's a power play and he is holding his money over you for manipulation. If he actually wants to buy you something it should be the something YOU WANT.
He has to look at them all the time so it stands to reason that he should have a say:
How much time do you actually spend in the presence of your partner vs out in the world with coworkers, friends, strangers on the bus, in the coffee shop etc.? Is it more important that he feels attraction to the earrings he bought you than it is that you feel great (powerful, sexy, risky, playful...) in the earrings you are wearing in the world?
“They just don't fit with my vision of you”:
Well, people are CONSTANTLY changing! You are, he is, the trends, fads, accepted norms, seasons, aging, life circumstances, jobs..... It is said that the only thing you can count on is change. So, like, get with the times bruh. Try to see your lady as the free, independent organism that you fell in love with way back when.
“She trusts my opinion more than her own”:
Um, that's a problem.... because she should be encouraged (by you, her partner) to experiment, try out different styles, colors, lengths and find what makes her FEEL great. Yeah, sometimes it's about appropriateness for the situation and context, but those rules are flexible (unless you're, like, the Queen of England or something.) and often times the edgy choices get you noticed! And if you don't want to get noticed, well, pull your hoodie up I guess. The point is, relationships are about personal growth, accountability, and support. If the dynamic is one that disempowers her to make her own decisions about something as personal as what earrings she likes then your relationship is highly codependent and unhealthy.
“I'm afraid if he doesn't like what I'm wearing he won't be attracted to me”:
Are You the clothes you wear? Is he? On the weekends does he wear cargo shorts, flip-flops and an old teeshirt he got from volunteering for a 5k three summers ago? Do you still want to fuck him? Do you find him attractive in spite of this? He can get over it too. If you like the way you look, you will FEEL sexy which makes you exude sexiness and that has nothing to do with your jewelry, clothes or hairstyle (in spite of what the grocery store checkout line mags say). Sex appeal and attractiveness are a state of being.
You be you! The person who actually truly loves YOU will love the confidence you exude when you wear what makes you feel magnificent!