I remember when I was ten years old having a small collection of trout flies (which I never got to use, since the only places I could go troutfishing were brooks closely overgrown with small trees and bushes.) The prettiest of them was called Dolly Varden, though I did not find out why until many years later, when I read that it was because she was excessively fond of many bright colors in her clothing.
I now suspect the fly tiers liked the colors of the lure better than any trout ever did.
I'm almost halfway through Barnaby Rudge, and so far all Dolly Varden's color has been limited to a cherry red ribbon on her hat.
I searched for picture of Dolly Varden trout flies but couldn't find any. I was surprised to learn that "Dolly Varden" is also a variety of trout. I wonder which came first.