I double-checked my "Spirits" cup, and indeed, the rough clay has nearly the same coloration whether glazed or not (well, except for the thicker parts of the glaze that turn blue). I suppose you *might* say that the interim part of the glaze (where the blue is very, very faint) causes the clay to look a bit grayer, but not by much.
And I'm not seeing any major difference near the crackles.