18 Stunning Nontraditional Celebrity Engagement Rings 2015. Diamonds may be a girl’s best friend, but for some celebrities a regular solitaire sparkler just doesn’t cut it. Instead, stars like Elizabeth Hurley and Rebecca Romijn have opted for colorful stones in hues like canary yellow and sapphire blue. Even in the past, Princess Diana forwent a traditional diamond for an oval sapphire, which Kate Middleton now wears. And in recent months, a new trend has popped up — art-deco-style engagement rings — worn by actresses like Scarlett Johansson. Keep reading for some major ring envy, and if you can’t get enough, see these very best celebrity engagement rings, then check out which of your favorite stars have been in their famous friends’ weddings.