Color theory primary colors work at all is that the imperfect pigments being used have sloped absorption curves, and thus change color with concentration. A pigment that is pure red at high concentrations can behave more like magenta at low concentrations. This allows it to make purples that would otherwise be impossible. Likewise, a blue that is ultramarine at high concentrations appears cyan at low concentrations, allowing it to be used to mix green. Chromium red pigments can appear orange, and then yellow, as the concentration is reduced. It is even possible to mix very low concentrations of the blue mentioned and
Orange (colour) also widely worn by workers on highways and by cyclists to avoid being hit. A herbicide called Agent Orange was widely sprayed from aircraft by the Royal Air Force during the Malayan Emergency and the US Air Force during the Vietnam War to remove the forest and jungle cover beneath which enemy combatants were believed to be hiding, and to expose their supply routes. The chemical was not actually orange, but took its name from the colour of the steel drums in which it was stored. Agent Orange was toxic, and was later linked to birth defects and other health