Origin of Phrases - H
Horse of a different color
Meaning: Unlike the subject at hand.
Example: Bush and Reagan are both credible, but Bush Jr. is a horse of a different color.
Origin: Horses are registered at birth and the registration includes a record of their color. When a horse trades hands due to sale, the registration is also transferred. Sometimes the color recorded on the registration may not match the actual color of the horse leading one to suspect the horse is not the one in the registration.
Horses sometimes change color as they age, just as some people's hair changes color. More likely the horse is not the one represented on the registration but is actually an entirely different horse.