Ah, then the error must be on my end. I thought GreyMatter was a SuperPewter Pied.
If GM does have Champ then my bet is the animals in question are Champagne Calico Pewter. The Champ Pastel looks very similar upon hatching and the synergy of Calico wiping out pattern when combined with Pastel is also pretty common so stacking those three together I can see leading to a whitish snake