Here's a pictorial example. I don't know what to say in terms of solid evidence except to say, look at photos of blue chicks, then at partridge or blue partridge or duckwing chicks, then. . . Here's an Araucana (well, I had many) that looked blue at first then feathered out and some, the splashes especially, had the duckwing stripe on the head like yours. As they matured, some looked promising, but by 5 months old they all had definite signs of duckwing in the background - yellow, silver, or gold/red leakage down the neck, shoulders, saddle, etc.
A truly solid blue bird as a chick will be solid blue with yellow or white underside. There will be no black stripe down the eyes, the forehead, or the main body. The black stripes indicate duckwing or partridge, as you may notice with such colored birds, they look like chipmunks. Add some blue genes to one and cover up some of the duckwing with some extended E/E coloration (basically solid blue, black, or white) and you've got just partial yellow, red, or striped patterning left, which usually shows up in the facial area. As the chick matures, it will confirm this mixing of colors by feathering out colors other than just blue. (yellow, red, brown, etc)
Ah and to help, here's a Splash with the duckwing influence. . . Notice the stripe on the eye and head. Big red flag markings there
Thank you. So what color should my blacks be? Solid black or is some white on them acceptable as chicks? Is it possible for perfect looking parents to throw imperfect chicks?? I'm confused about that.
A black chick naturally will have white on the underside. Ameraucanas may have solid black color, white on the underside, or even a slight yellow hue under there too.
Perfect looking parents passing imperfect chicks. . . Yes, it is possible. There are things like recessive traits that can pop up, and, in cases like color leakage, females usually don't present it physically. I wouldn't worry too much though. If you like your chicks, all is okay. If you want purebred Ameraucanas, the blacks look fine to me. Only time will tell with those. When it comes to other genes hiding in there or color leakage, blacks are hard to tell until they're older. Blues are a little easier. Splashes as you can see from my chick photo are very easy.