Fluff color on adult birds

[Blisschick]

I'm trying to recall a rule I learned awhile back, but seem to have forgotten:

Is it that adult roosters that are dominantely wild-type (BBR) have gray down, and partridge and wheaten have white? I know it's either that or the other way around. I do remember the best way to tell is to look at the fluff at the base of the tail.

 

[Kev]

White down= BBR is what I heard. With the caveat that there can/may be various genes that alter the down color though. What these are, don't know.