International orange is the official name of the color used for things such as
hunting jackets,
construction worker's vests,
crossing guard uniforms, and all manner or
cautionary signs, including but not limited to
construction signs,
traffic cones, etc.
International orange is, as defined by the International Color Consoritium (www.color.org), fluorescent orange with a dominant wave length of 595-605 nm (a measure of light intensity), a purity of not less than 85 percent and a luminance factor of not less than 40 percent. There are many regulations concerning the shade of orange used on these items, as well as other aspects such as reflectibility (on vests and signs, retroflective tape or film is used), which shade to use if the object is going to be outside during the day, which to use at night, and so on.
International orange is usually called fluorescent or Day-glo orange by the un-enlightened.