Carnage + Dilution = Shaded?

I may have encountered a possible combo marking/shape mutation in the scrying stone.

Because I was bored and I'm trying not to buy more wolves, I was wasting some money at the scrying stone. One of the possible pups that came up on one round for Shadow's current pregnancy really caught my attention because it looked silver (I want silver) and I didn't recognize the pattern. Curious, I went playing in the wardrobe and determined it was the shaded marking, and likely silver given the depth of the "shine" it had. Sadly I didn't have the good sense to take a screenshot.

Anyway, neither Shadow nor the stud has the shaded marking, and the only place they have the opportunity for a silver anything is slot 2, where Shadow has black carnage and the stud has white dilution.

Is this a known thing? I'm new to the whole combo markings thing.