Tigers and blue bars usually develop that way. They start out with the dark to black coloring on the far sides of their back after a shed or two. And then with more sheds the tiger starts to be more prevalent or the blue bars.
I haven't bred for as long as AHBD did, but I've bred quite a bit, and followed many breeders and this is what we see from certain pairings.
Unfortunately Josh's fb got taken down so I cant find the pictures of the few black babies hes made (and I mean jet black, full body, no lines down the back, no other colors, just black) and they always lighten. It's from a mix of the zero wit and trans Gene's. And as far as I'm aware, its mainly the trans gene that does it.
And with all trans babies, the visual trans traits start to fade with growth. That's why trans hatchlings are almost see through with their blue bellies, but that never sticks around more than a few sheds.
In some Weros, there is black marbling that seems to stick around better, but it too lightens up a bit. And it's just marbling not full black.
Here is a pic of one of his marbled weros which he sold for 1700 lol
And here is one of the darks he produced. It's the only pic I could find and is probably only half as dark as ones hes done in the past:
His comment under that picture is the trans zeros always lighten with age into a grey color.
As far as I'm aware, hes the only one who has even came close to anything resembling a black dragon. And I follow a lot of breeders lol.
But, grow them out and see how they turn out. Its interesting anyways to see how they can change.
For instance, some of the deep saturated reds start their first few months of their life as a dookie brown color lol.
And blue bars typically look like yours until a few more sheds.
-Brandon