colour bar

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The segregation of people of different colour or race, especially any barrier to black people participating in activities with white people.
• noun printing A pattern of varying tonal density that enables visual and numeric comparisons to be made across multiple printed sheets or pages.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun barrier preventing blacks from participating in various activities with whites