A few folks that are participating in the large fowl splash approval process have asked for pictorial examples of the difference between rust and brassiness.
Brassiness is a serious defect that is defined as a light yellowish metallic cast particularly in the hackle, wingbow and saddle of the male that can be hereditary or affected by exposure to sun rays or certain items in the diet. A defect is anything short of perfection.
Rust is a disqualification that is reddish brown in color. A disqualification is a term applied to a deformity or defect that is serious enough to debar a fowl.
Hopefully this post will be of help to you as you breed your large fowl splash Ameraucanas towards the proposed standard.
Thank you to the APA for giving me permission to use excerpts of the standard when creating educational posts. An APA Standard of Perfection book can be purchased at the following link and goes into detail on the Ameraucana breed, the standard for the approved varieties as well as defects and disqualifications in poultry.
http://amerpoultryassn.com/sample-page/apa-store/