Timber Man,
Here is my .02 on this subject. My theory is that steelhead and salmon feed on shrimp in the ocean. They get immune to them upon returning to fresh water. The shrimp are white in color and the white backer rod represents a shrimps body. The yarn represents legs or whatever. I know for a fact that the ear plugs work, but in my opinion they don't hold scent very well. The other colors mentioned, such as light pink and pink and others will work. The grey and light green I tend to stay away from though. This is just my .02 take it however you would like to.

Thanks,
Andy Matthews