That happens whether they eat gro-gel or not. Wing feathers start coming in very fast on some chicks.
If they have a yellowish dot on top of their heads, barred.
If no dot on top of their heads, black.
Although "black" may not be quite accurate-- they could be solid black, or they could have various amounts of leakage of other colors (example of a possible coloring: Black Sexlink hen are "black" but often have large amounts of red in their breast and neck feathers.)
You might be right about the coloring, but there is also a chance they could be more varied in appearance than you currently expect. For example, the yellow chicks could be white or wheaten-- but they could also be silver wheaten, or columbian, or buff columbian, or some mixed-looking color that isn't quite like any of those. And chipmunk-striped chicks can grow up to have some variety of appearance too: with silver or gold in their coloring (gray/white shades rather than red/gold shades), and sometimes other color patterns than the one you mentioned (example: Dark Cornish adults are a dark red with black double lacing, but they look chipmunk-colored at hatch. I don't expect any Whiting True Blues to look exactly like that, but it is an example of another adult appearance that has chipmunk striped chicks.)
I would love to see photos as they grow, because I'm also curious about how they will look
I should hope not, given this part of the description on their website:
"Whiting True Blues are not Araucanas, Ameraucanas, or 'Easter Eggers' — they are their own breed named after the poultry geneticist* who developed them."
If they want to consider WTB a distinct breed, then they should not be mixing them with anything else. (I do not know what they actually do. This is just my opinion about what they should do.)