a horse of another

horse of another 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 another color.
See also: another, color, horse, of
Farlex Dictionary of Idioms.

a horse of another

/a different color
Another matter entirely; something else.
See also: another, horse, of
American Heritage® Dictionary of the English Language, Fifth Edition.
See also:
  • 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
  • all righty
  • a straw will show which way the wind blows
  • a crack at (someone or something)