Regarding the Wheaten chicks, The old thought was that the chicks had to be completely free of color in order to be true Wheatens. Anything that had color was considered a mis-colored chick and would produce a mis-colored adult. But there were lines that hatched with spots and or stripes on their head and back that grew out to be nicely colored, with very little black stripping in the male hackles. So the point was made that the lines could be different, have different colored chicks, and still produce good colored adults. Studying and knowing your line, means you can reasonably make early assumptions. The beauty of this knowledge is the ability to know what to expect from the chick down and be able to make decisions earlier rather than later. If you bring in new stock, you introduce unknowns that will cause this knowledge to be upset/changed. And the breeder again has to question the tools that they have used in the past and begin over again.
But also I think in understanding chick down early in the process you can begin to make assumptions about the genetics as Harry is discussing with Blacks/blues. If you get chicks from your blacks that are all ranges of patterns, penguin colored, more solid black and everything in between, then you likely have a mixture of E/E^R genes working in your breeders. You will get a variety of colored chicks and will not be able to reliably predict the likely result. If all of your chicks hatch in one pattern, then you have a much better chance of understanding the underlying genes at play. And this helps the breeder in making decisions with the line.
BTW Harry, I am glad that you are finally making the progress in your line again this year. I know its been a long road back from the predators destruction. What do you look for in the chicks from your line?