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  2. Emergency vehicle lighting - Wikipedia

    en.wikipedia.org/wiki/Emergency_vehicle_lighting

    In Arkansas and Kentucky, civilian possession of a blue flashing light is prohibited by state law. Additionally, blue is the color used by law enforcement agencies. In California, all emergency vehicles just use red warning lights, with 1 steady red warning light facing forward.

  3. Wratten number - Wikipedia

    en.wikipedia.org/wiki/Wratten_number

    Wratten number. Wratten numbers are a labeling system for optical filters, usually for photographic use comprising a number sometimes followed by a letter. The number denotes the color of the filter and its spectral characteristics, and these numbers can be grouped into broad categories, but the numbering system is arbitrary within a group and ...

  4. List of U.S. state colors - Wikipedia

    en.wikipedia.org/wiki/List_of_U.S._state_colors

    Blue: Yale Blue, cable number 70086, Standard Color Card of America, 9th edition. Gold: Golden Yellow, cable number 65001, United States Army Card of Official Colors for Arms and Services. Yale Blue: Deep purplish blue. Golden Yellow: Vivid yellow.

  5. Vehicle registration plates of Arkansas - Wikipedia

    en.wikipedia.org/wiki/Vehicle_registration...

    The U.S. state of Arkansas first required its residents to register their motor vehicles and display license plates in 1911. Prior to 1911, plates were issued by cities. As of 2022, plates are issued by the Arkansas Department of Finance and Administration. Only rear plates have been required since 1944.

  6. Infrared photography - Wikipedia

    en.wikipedia.org/wiki/Infrared_photography

    Green band wavelengths form cyan and magenta dyes to produce a blue color. [15] Blue light is typically to be blocked out using a yellow filter. This is because the biased sensitivity towards short-wavelength radiation, characteristic of color infrared films, makes exposure to blue light undesirable, and unintended by design of the emulsion.

  7. Biological effects of high-energy visible light - Wikipedia

    en.wikipedia.org/wiki/Biological_effects_of_high...

    Blue light, a type of high-energy light, is part of the visible light spectrum. High-energy visible light (HEV light) is short-wave light in the violet/blue band from 400 to 450 nm in the visible spectrum, which has a number of purported negative biological effects, namely on circadian rhythm and retinal health (blue-light hazard), which can lead to age-related macular degeneration.

  8. Red states and blue states - Wikipedia

    en.wikipedia.org/wiki/Red_states_and_blue_states

    By 1996, color schemes were relatively mixed, as CNN, CBS, ABC, and The New York Times referred to Democratic states with the color blue and Republican ones as red, while Time and The Washington Post used the opposite scheme. [16] [17] [18] NBC used the color blue for the incumbent party, which is why blue represented the Democrats in 2000.

  9. Optical filter - Wikipedia

    en.wikipedia.org/wiki/Optical_filter

    An optical filter is a device that selectively transmits light of different wavelengths, usually implemented as a glass plane or plastic device in the optical path, which are either dyed in the bulk or have interference coatings. The optical properties of filters are completely described by their frequency response, which specifies how the ...