Champagne is caused by the dominant gene Ch. It affects bay, black, brown and chestnut when it is Ch?. A chch horse posesses no copy of the gene.
The champagne causes the base coat color to lighten.
Chestnut dilutes to Gold Champagne, bay to Amber Champagne, brown to Sable Champagne and black to Classic Champagne.

The Champagne Gene causes pink skin around the eyes(?), and the base of the tail.
The pink skin of a Champagne horse is "pigmented pink" — not the pigment-free paler pink color found under all white markings of all horses. It may tan.

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