Kate wore this bracelet to the 2006 Boodles Boxing Ball.
Here is the closeup:
I’ve been trying to properly name this color. It looks like a stormy deep blue with tones of green.
But in this photo, it looks more teal.
The bracelet is made of capsule-shaped stones (possibly quartz) set in gold plated metal and linked by four gold metal beads on each side of each capsule. I am assuming this is a stretch bracelet.