Mallard and Claret is an olive pattern. Over the years I have tried many colours from brown to black to claret but I always come back to a decent greenwell hen hackle tied over the wing, with as black a centre as possible.
The black centre creates a solid head point which I like to achieve on all my olive dressings but at the end of the day its down to what you personally prefer. Again, quality of hackle is the main issue. Its also a regional thing...........one colour may work better in one area than another.
Cheers George

PS

To enlarge the debate, I don't like bronze mallard as a wing on my M & Cs
Give me a blae wing on all my olive patterns.