White horse - meaning no pigment.. but has grey mottled nose

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technically speaking shouldn't this horse be solid white? Even on Appaloosa patterned horses you don't see a mottled nose. I was told that the mottling is normally a sign of Ch (upon gene testing she is) however I have never noticed white horses having anything other than a pink nose and am wondering if this is a bug. I found another SH with the same nose, who also has the potential to be Ch but isn't gene tested.. I haven't found this with any other breed

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is this just a white hiding Ch thing or is this a layering bug