This is a limited edition polish from the Sally Hansen Hard As Nails Xtreme Wear line. The display didn't specify a season and it started popping up in July and August, so I'll say it's from their Fall 2010 collection.
Purple Gala is a sparkly foil with purple, silver, and gold glitter in a smoky purple base overlaid with lots of larger gold glitter pieces. You'll see more purple versus more gold depending on the lighting. This polish was opaque in 2 coats, but I put on a third coat for a little more depth.
This was a challenging polish to find even after it was recently released. Since that was almost a year ago and this is a limited edition shade, it might be near impossible to get Purple Gala now. But never fear! If you like the look of Purple Gala, I recommend picking up Hard Candy's Mr. Wrong, which is close enough in color and finish to be a dupe to the casual observer.