color bar

/K AH1 L ER0 B AA1 R/
noun
  1. 1

    The segregation of people of different colour or race, especially any barrier to black people participating in activities with white people.

  2. 2

    A pattern of varying tonal density that enables visual and numeric comparisons to be made across multiple printed sheets or pages.

  3. 3

    (jewellery) In a rough opal: a layer of good jewellery-quality opal.

Source: https://en.wiktionary.org/wiki/color%20bar, https://en.wiktionary.org/wiki/colour%20bar