A horse of a different color

Meaning

A matter entirely different from the one under discussion.

Usage

Used to signal shifting to a distinct topic.

Origin & History

Origins and dates here are approximate summaries. Many idioms have disputed or unknown origins, and not every date has been checked against a historical dictionary, so treat specific dates and stories as a starting point rather than a citation.

Echoes Shakespeare's Twelfth Night (about 1601), which has the line 'a horse of that colour'.

Shakespeare's line dates from around 1601; the modern wording became common later.