I think that you can be pretty safe with black white and grey. Seeing as they’re classic colours, I don’t think anyone will think twice.
But I do see your concern, most people will go with yellow or blue as it goes with the beach, but I think that as long as you keep it casual it won’t look out of place.
The closest I’ve seen to this is this wedding:
The bridesmaids are wearing really light grey dresses which is a lot less intense and I think looks beautiful so you might want to consider that if you want to stick with your theme.
I hope that helps! And congratulations! Please send some photos in after the big day - I’d love to see some :)