From the designer, Tyler Boroff:

Midges are always on the menu for trout. Most midge larvae have a tapered look to them and are generally big headed. Using a purple glass bead as a head with a slow taper back seemed to grab the most attention from the midge crazed trout. Adding a very subtle hot spot just behind the bead helped key in on the small bug in fast off colored waters.Trout can’t help themselves when it comes to purple.