Most of the time I use dubbing as the shuck - the fibers of most dubbing now are a multitude of colors with one predominant color. I also trim them at an angle rather than square, since bugs don't have square butts. I've been promoting angled shucks for years and just saw Craig Matthews of Blue Ribbon Flies trim one of his fly's shucks at an angle.

Here are a few examples:

Amber shuck for a BWO:




Amber or gray for midges:


Rust for PMD's: