Yes, a few people suspected he was champagne, but he's incapable as far as I know, because one parent would have to be.
That said, his grandmother (Dell Tera's Betty) is one of the last known living daughters of Dell Tera's Hippy, who is a known champagne ancestor.
I think it is just the interaction of silver and creme dilutes, though it IS fascinating. His full brother had blue eyes, also, and the same interesting sheen in his coat, though Comet was a palomino in appearance (same smoky black stallion X the same sorrel carrying silver mare).
Liz