# The Road Vehicles Lighting Regulations 1989, Paragraph 2


...The colour of rear retro reflectors fitted to a vehicle used for—
(a) police,
(b) Scottish Fire and Rescue Service or, in England and Wales, fire and rescue authority,
(c) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(d) Driver and Vehicle Standards Agency, or
(e) traffic officer,
purposes may be red, yellow or orange (or any combination).

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Source: https://www.legislation.gov.uk/uksi/1989/1796/schedule/18/paragraph/2 (the official version)
Page: https://openlegislation.uk/road-vehicles-lighting-regulations-1989/schedule-18/paragraph-2
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.