I use black estaz twisted together with black chenille for flash buggers, not the material, it's the method it's fished.  A couple of wraps on a 1/0 and you know what that method is. Haven't used black, but some of my best days have been on large blue estaz eggs.

Fichy blue estaz with a red back pulled from the front to back over the top and tied off at tail have hosted many memorable steelhead days for me. Whether it be crystal flash, z-lon, or hi viz... Pink, orange, and chartruese for tail color or backs have been comparable... Something about that blue and red though especially in cold winter months

fichy, you're giving away the secret sauce.