Here's one of the QRS shades I ordered recently, and I think it works nicely as a top coat. It's called Glittering Rainbow, and it's packed full of tiny multi-colored holographic glitter in a clear base. I used one coat over Jessica Purple Burst.
Above & Below: The top picture was photographed outside under partly cloudy skies, and the photo below was taken using a flash. The last photo is with no flash taken indoors.