The backs of all the Beijing 2008 medals are inlaid with a ring of jade.

The gold medal has white jade (I think) and I can't even remember/picture the silver medal's component. I think it's kind of gray or off-white

The bronze medal features the nice deep green that I've always associated with jade, and is by far the best-looking of the three when seen from the back side. Best-looking to me, anyway; I can clearly visualize it, whereas I can't conjure up an image of the silver medal's back side.