# Geneva Conventions Act 1957, Paragraph 4


The recommended blue colour is obtained when its chromaticity is within the boundaries of the International Commission on Illumination (ICI) chromaticity diagram defined by the following equations:
green boundary
y = 0.065 + 0.805 x;
white boundary
y = 0.400 a x;
purple boundary
x = 0.133 + 0.600 y.
The recommended flashing rate of the blue light is between sixty and one hundred flashes per minute.

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Source: https://www.legislation.gov.uk/ukpga/Eliz2/5-6/52/schedule/FIFTH/part/VI/chapter/21/paragraph/4 (the official version)
Page: https://openlegislation.uk/geneva-conventions-act-1957/schedule-FIFTH/part-VI/chapter-21/paragraph-4
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.