Ace Young presented his longtime love with a diamond, yellow gold and platinum ring

Courtesy David Webb; Inset: Frank Micelotta/Picturegroup

What a gem! For his surprise proposal on
American Idol
Wednesday night, Ace Young selected an 18-karat yellow gold, platinum and diamond engagement ring to present to longtime girlfriend Diana DeGarmo.

The David Webb sparkler, which features a 1-carat fancy yellow center stone, also boasts two side diamonds weighing .2 carats.

Young helped to design the ring, after hearing DeGarmo drop a hint. “A month ago, she said, ‘Gold needs to come back,'” Young told PEOPLE after Wednesday’s finale. “I was like, ‘I agree,’ so mental note. Her favorite thing is a sunflower and she loves yellow, so one of our dear friends [helped me] put together a ring that has a yellow diamond, a gold band and two smaller diamonds on the side that are clear, so it’s like a sunflower.”

The couple, who’ve been together for two years, met in the spring of 2010 when both signed on to costar in the Broadway revival of the musical Hair. DeGarmo appeared on Idol season three, while Young was on season five.