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In page Color blindness:

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There are several other features of traffic lights that can help color-blind people. British Rail signals use more easily identifiable colors: The red is blood red, the amber is yellow and the green is a bluish color.[citation needed] Most British road traffic lights are mounted vertically on a black rectangle with a white border (forming a "sighting board"), so that drivers can more easily look for the position of the light. In the eastern provinces of Canada, traffic lights are sometimes differentiated by shape in addition to color: square for red, diamond for yellow, and circle for green (see image).