You could be right. I raise light Sussex as well and was also using some classical references for this breed. "Registry of Poultry and Genetic Stocks" Ralph Somes, Poultry Genetics, Univ. if Connecticut, published 1978. Describes this breed and designates the genetic make up of the breed and the plumage patterns. He references two articles on how Columbian restriction pattern works, Journal of Heredity1965, 56

g 150-156 and Journal of Heredity 1970, 61:280-283. However, some breed patterns have changed if other genetics have been introduced. If the breeds have been maintained 'pure' from their origination then they 'should' carry the designated patterns that were determined through genetic testing. But knowing how much cross breeding goes on, the base genetic make up could be different.
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Hi Bentley,
I have also been doing a lot of classic study on Light Sussex. Such a rich literary history of this breed. Just another thing that drew me to them, smile. There's a confusing alliteration back in the early part of last century. People seem to be giving breeding advice which doesn't match up with what we see in our birds today. Yet the advice is coming from honored veteran breeders of that era. I think I am starting to figure it out. As you know, there is a lot of Light Brahma in Light Sussex foundation. Sharpe (see book Sussex Fowl , on-line at archive.org). Sharpe was the originator of the Light Sussex and we get some clues in his book. OK, Light Brahma are an eb-based breed. Plus there is also Buff Cochin in Light Sussex. If I read Sharpe correctly, the sappiness was coming from the Buff Cochin. The black ticking on the saddle and other parts was coming from the Light Brahma. The Silver Grey Dorking, obviously, was the culprit for the 5 toes they needed to breed out of the Light Sussex...however, also made the Silver gene available to the fancy.
OK, so I think the Light Sussex was accepted by the English Sussex Poultry Club (which was founded in 1903) about 1906? and by the British Poultry Club circa 1913?. I think I am close on that.
So early on, we start seeing all this counsel on depth and hue of undercolor and how it effects top color. How to deal with sappiness and breed it out. I think the fancy was still dealing wit the residual effects of eb and buff in the Light Sussex. But because they are still describing their breeding efforts as "The art of breeding" they describe colors and their interaction instead of the genes behind them. I am not even sure the genes had been ID'd at this time in history.
OK, so gradually we see them stop discussing sappiness and the discussion on under-color begins to evolve from depth and hue....to pure white and how to color balance the hackle in male and female. Then about the time the genes for Light Sussex, eb and buff , etc., get IDed and the info scattered around the fancy, we stop seeing the discussion about sappiness, and under-color at all. Now it is all about color balancing the black and white in both sexes. The only references we see to undercolor at all have to do with it's effect on color balancing the hackles in both sexes.
What happened? I think, unbeknownst to the Light Sussex fancy...because they were using the "art of breeding" and going by visual results instead of genetics....I think the fancy ( while trying to solve the sappiness, undercolor, and ticking problems) bred out the eb locus and buff gene, leaving just Silver and Co on a pure eWh base. I am not sure they knew what they had done as defined by genetics ... more the results just lined up with their goals.
Later on, the scientists gave names to the genes in Light Sussex. By then, the Silver gene was established in the Light Sussex. So unless we go back and study how the terminology of that era was changed and shaped by the collison of the two fields of breeding, the
art of breeding, and the
genetics of breeding, it seems difficult to understand the color history of the Light Sussex. I've been muddling thru this confusion for over a year now and it's just starting to make sense.
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Think it's the same thing with the APA versus English description of the Light Sussex hackle. Britain says white feather striped with black. APA says black feather laced with white. They really are kinda two different things. But why? Why the difference? Well, back when Light Sussex were being shown and considered for APA SOP, the folk in Britain were having trouble with a fad for superhackle. Outram talks about it in his 1920's book. I have a copy here. However, the top show birds of that era were what was being shown in the US. I think the APA folk went by what they saw. Certainly makes sense from an APA standpoint. And I think what they saw was these superhackle Light Sussex. So, while the fancy in Britain eventually came back to center and began breeding correct hackle once more. By then, the APA had written the Standard as a black feather laced in silver because that is what a superhackle looks like. Fortunately for today's breeders, the APA did not assign ratios to black and white in the hackle feathers. So we can breed to either description and still be acceptable at the shows. The lacing will just be wider in some cases than in others.
Plus we now have the genome for the Light Sussex so it is obvious to breeders that the proper hackle is made by using Co correctly and not using any other genes which might promote lacing of feathers.
Gotta love that breed history,
Karen
Moral of the story: Pick and choose coor breeding info from that early era, however the structure breeding info is great, classic, timelesss....click, drool.