Odd one out

Can you spot the odd one out?

I had an hour or so to kill between seeing Tam O'Shanter (REALLY good show by-the-way) and The Oxford Gargoyles - Jazz a Cappella! (another REALLY good show!), I took some time to wander up and down the Royal Mile with my camera and the "Gargoyles" were actually singing on one of the small stages on the Mile (about 1/2 an hour before their show), I stopped to take a couple photos.

All the singers are dressed in very smart outfits, the young men in black formal suits and the young ladies in little black dresses, however I couldn't help notice one of the young ladies footwear was a little different (today WAS a bit wet).

I should add she was NOT wearing these at the actual show.