I agree. I think,... I have to find reference for this,... I think,... if you are getting brassiness in your eb (Brown) based Columbian Rocks, it's because there is not a correct balance in the hue of the underfluff and it is affecting the top color of the plumage. As catdaddyfro said, there is no autosomal red or eb in WR.
Best,
Karen
Like my Leghorns, there are plenty of WR's with dominant white that will not be affected by sun or corn. Yellow corn will change a Leghorns white earlobes yellow...along with making their legs a brighter yellow, so corn is doing something to color...just not to dominant white birds. Yellow corn can also cause purple barring in some black birds.
Walt