What a friend of mine did was she asked her attendants to wear navy, but whatever style was comfortable. Most of us wore outfits we already owned. The men just wore plain dark suits and white shirts. She wore a cream pantsuit because she hates dresses and her husband wore a pinstripe suit.
It was her second marriage. She’d been forced by her parents to have an extravaganza the first time around and she was determined to have things as fuss-free as possible the second time around.
My boss got married in Hawaii. Photos of his wedding show that all male attendees wore Hawaiian shirts, shorts and flipflops. All the women wore bright Hawaiian print dresses of their own choosing.
Exceptions: the bride wore a long, somewhat fancier floral print dress, and my boss wore long chinos rather than shorts.