I need to design jewelry for someone's wedding. This may be a dumb question - but - the bride should be the only one wearing white - is that the "etiquette"?
I think that only applies to the dress. That is, no other woman should wear white clothing... I don't think jewlery really counts, as it is not as eye-catching as someone other than the bride wearing white. I think that as long as you stick to the bride's requests for color or style or both, you'll be fine.
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"I base most of my fashion taste on what doesn't itch." - G. Radner
The most traditional thing you see is for all bridesmaids to wear pearl neckalces, which I would put in the white category. For me personally I love pearls mixed with a gemstone that matches the bridesmaid dresses and a more dramatic necklace for the bride.