I don't think Fred will throw us out of class for getting off topic.... (go easy on us professor)I wonder if Scott's statement about brassiness could be what is going on with Delawares? I guess that is a bit off the subject at hand.
If your Dels are showing brassiness in the hackles, shoulders, saddles then it is probably the same issue. Apparently, the are "inhibitors" that keep brassiness from expressing itself in silver columbian based birds. It seems that it requires 2 copies of Aph~I to suppress this in the males and 1 copy in females.
In my case, I was advised that the "Old Heritage Lines" of Barred Rocks were carriers of 2 copies of the inhibitor Aph~I and that is what I used to cross into my line. I was also told that a White Leghorn also carries the inhibitor if that breed is more available to you.
Those articles in Exhibition Poultry explain it in a lot more detail, but hey, I'm a "genetics neophyte"....gotta boil it down to laymans terms