High-visibility colour
A very bright fluorescent colour, usually yellow-green or orange, worn to be seen easily.
Also: hi-vis, safety colour
Road workers, cyclists, railway staff and emergency crews wear high-visibility clothing so that drivers notice them early. The colours are fluorescent, most often a yellow-green or an orange-red. Fluorescent dyes turn ultraviolet in daylight into extra visible light, so the fabric looks brighter than its surroundings, especially at dawn and dusk. Yellow-green lies close to the wavelength the eye is most sensitive to. At night the colour does little, so garments also carry strips that bounce headlight beams straight back towards the driver.