It does look like a tattoo to me. But, oh well, Charlene is not posh.
If that is a tattoo and not just the trim of her suit, then that is a great example. Something almost never seen in public, not going to offend any ultra conservatives shocked by a woman with ink, at an event.
The Palace has released a video to mark the 15th anniversary of Prince Albert's enthronement today, July 12:
** video **