horse of a different color, a

horse of a different color

Something completely different or separate, especially in comparison to something else. I've always found math to be easy, but calculus is a horse of a different color.
See also: color, different, horse, of
Farlex Dictionary of Idioms.

horse of a different color, a

Also, a horse of another color. Another matter entirely, something else. For example, I thought that was her boyfriend but it turned out to be her brother-that's a horse of a different color . This term probably derives from a phrase coined by Shakespeare, who wrote "a horse of that color" ( Twelfth Night, 2:3), meaning "the same matter" rather than a different one. By the mid-1800s the term was used to point out difference rather than likeness.
See also: different, horse, of
The American Heritage® Dictionary of Idioms by Christine Ammer.
See also:
  • a horse of another
  • a horse of another color
  • a horse of another colour
  • (you) wanna make something of it?
  • a fast talker
  • (you've) got to get up pretty early in the morning to (do something)
  • a/the feel of (something)
  • (I) wouldn't (do something) if I were you
  • a straw will show which way the wind blows
  • a crack at (someone or something)