The champagne gene is dilution gene distinct from the cream gene (which is responsible for buckskin & palomino) that can produce similar colors. They can be hard to tell apart from far away, but up close they can be distinguished by things such as hazel eyes & freckled skin (which the cream gene does not cause). The "champagne version" of buckskin is called amber champagne, and the palomino version is called gold champagne. Champagne also shows up in black horses (creating the color 'classic champagne') whereas cream does not show up on a black coat.
Some more reading: Champagne gene - Wikipedia, the free encyclopedia