@Zawisty, I saw you mentioned Autosomal Red. I have this in my Silkies, Silkie crosses, & OEGBs.
I usually see it in the hackles, saddles, & shoulders. I have some examples if you'd like I can share some pictures?
I'm still learning too.
Light Sussex is one I just haven't learned much about. I guess the breed has really hasn't been much of an interest.
I read Genetics forums here, & from other chicken sites, articles/studies.
Okay, they're a yellow white color.
I did go back to the place I found. I missed a part of the discussion. According to them they're Wheaten based too.
Never mind. Juvenile plumage just didn't seem to fit when I was looking around.
Here's a few 5 week olds.one of my Partridge based silver Columbian chicks.(Old picture)
I did find one place discussing their genetics also. I'll have to find it. Information is scarce for the breed genetics wise.
Looking at juvenile plumage of the Light Sussex shows some partridge patterning on the backs. But not all chicks will leak pattern in juvenile plumage.
But I can do some more digging around, to double check.
I don't know tons about the breed.
I'm not an expert on dominant white, but I know that it's abit difficult to prevent leakage of certain colors, like red, or occasionally black.
I believe black helps the dominant white color be more even, & have less leakage. I maybe wrong though, but not quite sure.