On a wedding party, beside new couples, bridesmaids would be surely pretty scenery as well. And do you want to have a special party on your big day, to be unique and unforgettable? You can choose colorful dresses for your bridesmaid to decorate the party.
If you cannot accept your party to be too colorful, same color in different color tone would be a good choice. Since even in same color, different color system would create a different feeling.