Weird English Word

Rachel taught me a new word today. We were having coffee in my lunch break and I explained to her my new hairdo (not that I had to explain much tho, as I was in fact sitting in front of her).
Kat: It's really cheap, I got colour, cut and everything for 54 euros."
Rach: Yeah, I can see you've changed the colour. Nice!
Kat: Yeah, I finally got the dark highlights that I wanted. They always highlight my hair in a colour too bright and I never get the dark blond colour I want.
Rach: Lowlights.
Kat: ? Haha, yeah, lowlights. *good joke*
Rach: No, actually its' a word.
Kat: ? Lowlights?
Rach: Yeah. When your highlights are dark, it's called lowlights. There's no such things as dark highlights.
Kat: lowlights??
Rach: Lowlights.

Just when you thought you had your English covered...