In the safety programming of transportation, for ensuring safety, these divided into two categories: ICAO (International Civil Aviation Organization) and TDGR (Transport of Dangerous Goods Regulations). Moreover, solids, liquids and gases are usually authored Dangerous/Hazardous goods.
In the United States, dangerous goods are often indicated by diamond-shaped signage on the item, its container, and/or the building where it is stored. The colors of each diamond in a way has reference to its hazard, i.e.: Flammable is indicated with red, because fire and heat are generally of red color, Explosive is indicated with orange, because mixing red (flammable) with yellow (oxidising agent) creates orange. Non-flammable/Non-toxic Gas is indicated with green, due to all compressed air vessels being this color in France after World War II, and France being where the diamond system of HazMat identification originated.
If you are unsure whether your commodity is regulated by ICAO or TDG, please check your Material Safety Data Sheet (MSDS) for further information.