Because the bead is at the front of the fly it is this section that dives to the river floor first when the line is paused on the retrieve. After casting the fly try retrieve, pause, retrieve, pause. This helps animate the fly and makes them more attractive to the trout. If a sunbeam shines through the water it will reflect off the shinny gold bead head surface and hopefully help in catching the eye of a predatory trout. I prefer gold colored beads as I believe your chances of a fish taking your fly are improved.
Many classic patterns have gold bead head variations.
Have a great day.