These rainbow metal beads give a variable color as the fly swings or tumbles. Assuming the fly is high enough in the water column for the various colors on the bead’s spectrum to show with available light, I like the possibilities…
Same bead from different angles yields different color casts to the flies. There are several different sources for the metal beads.
SwittersB & Exploring 
Hi Jo,
These particular beads are made by Hareline Dubbin Inc. They are called Dazzle Brass Beads and come in a variety of colors, to include the Rainbows. The bead is a 3/32″. The beads usually come 24 per pack. I picked up the beads at The Caddis Fly Shop in Eugene, Oregon.
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