You can see the Albino Acid BlkPastel YB here. Fifth one down (I think), right before the Candinos:
And my dark beast is here:
I get what you are saying but, regular Snows are born pretty much white and the patterning on them is basically about underlying structural elements. As they age they develop a yellow hue to them in their patterned areas.
With what you are saying about the BlkAx, my guess is that that yellowing with age would be less likely to occur so the adult would retain the white on white apperance of the hatchling