Here is the worst from last year ... she makes a great example. I think she had a couple red feathers that popped out just before she reached POL last year. This summer, she molted and now looks like this ... (bad photo, they're free-range so I have to sneak up on them, and getting the lighting right is tough with an iPhone) ... her new red feathers look silver laced red? Ish? There are a lot of things I like about her, but clearly that color isn't breedable.
This one below is somewhat more typical of how the extra color shows up after the first adult molt, but I wouldn't breed her because of all the fluffy soft feathers anyway. That red/buff color is the same as our clay soil, so it is tempting to pretend she's just dirty. She's not just dirty. You can see the color shows up on the "top" of the bird, and it doesn't seem to go very deep. I *think* the fluff is okay. I've bathed a couple females, and the cape area can have extra black (gray) underneath that doesn't show up as obviously when the bird is dry.
When my starter females (from my starter trio) finished their first molt adult molt, they had about that much "bad" color, just a dusting on top, but it was barred white/buff.
If you look carefully at this year's pullets, you can find some with "salmon" color near the black. This presents more on pullets with the "strongest" coloring, meaning ones that have striped necks (instead of barred necks), or the ones with the "best" tails (meaning proper laced black tails instead of barred tails). Black tails tend to come with black necks in my flock. There also seems to be some correlation with leg color ... the birds with the most orange/yellow legs seem more likely to have the black tails & necks & salmon/buff/brown/red color show up eventually.
All of this seems FAR less pronounced in the males. We spotted very few cockerels with any hints of salmon so far this year. Color issues with the males are the typical "too much black" thing, though possibly there is gray encroaching into some of their fluff, too. POSSIBLY. That's just not something I've really looked into very much.
I really like the idea of working with last year's "white" hens. That's what my gut tells me to do. If I have a good cockerel this year, I might put them with him. They've already been with their father, and color was all over the place, though with a better selection process we might have better luck. Fingers crossed I also have one or two "white hens" with good type ... last year I was just too new to "going over" birds, and have crummy eyes for seeing up close, and wasn't able to table-top them, so kind of threw up my hands after culling for obvious things, and left 8 pullets in the breeding pen. Some were kind of sad compared to others. But it sure made gathering clutches nicer than when only working with a trio.
It is probably a good time of year, if there is such a thing, to ask @cpartist what she thinks. I really respect the careful work she's doing with the breed, and refer people to her if they're looking for chicks.