What is the name of the horse that changes color in the Emerald City?

The horse that changes color in the Emerald City is the Horse of a Different Color.

In MGM’s 1939 film, Dorothy and her companions see a horse whose coat appears to change from one color to another as they pass through the Emerald City. The visual joke is created by substituting differently colored horses between shots rather than by showing one animal magically transforming.

The gag comes from L. Frank Baum’s Oz story, although the film stages it as a memorable comic scene. The phrase is also a common English idiom meaning a fundamentally different matter, which can make the answer look like a general expression rather than a character or animal’s name.

The title is sometimes written with an initial “The,” but “Horse of a Different Color” identifies the same canonical Oz horse.