colour bar

Noun

colour bar (plural colour bars)

1. (UK) The segregation of people of different colour or race, especially any barrier to black people participating in activities with white people.
   • That first morning at the firm, a pleasant young white secretary, Miss Lieberman, took me aside and said, ‘Nelson, we have no colour bar here at the law firm.’1994, Nelson Mandela, Long Walk to Freedom: The Autobiography of Nelson Mandela, London: Abacus, published 2010, page 83
   • In my hometown of Portsmouth there was a riot in 1943, with the locals scorning attempts by American military policemen to enforce a color bar in the pubs.2010, Christopher Hitchens, Hitch-22, Atlantic, published 2011, page 205

   Synonyms:

   color line

2. (UK) A pattern of varying tonal density that enables visual and numeric comparisons to be made across multiple printed sheets or pages.
3. (UK) A layer of good jewellery-quality opal within a rough opal.