Carol - Hannah loves this bouquet. It has the amnesia roses, quicksand, and I guess white or off white. Since her dress is white, I would probably go with white. But she would also love dusty miller around the perimeter if it doesn't get too wimpy.
I have also seen similar centerpieces that use epsom salts instead of sugar. You could also sprinkle a mix of pearls/gems. Sand (or sugar), faux pearls, a 3 candle. An easy DIY wedding centerpiece idea.
Gems & Jeans - Water Gelatin with Blue Confetti and Floating Candles centerpiece. Do this with royal blue & bright green confetti, a few more pieces than the picture, and silver sparkles at the base instead of those confetti petals.