Dangerous goods are often indicated by diamond-shaped signage. The colors of each diamond in a way has reference to its hazard. For instance, Flammable = Red, Explosive = Orange, Non Flammable Non Toxic Gas = Green. Most countries regulate hazardous materials by law, and they are subject to several international treaties as well. Even so, different countries may use different class diamonds for the same product.
The United States Department of Transportation (DOT) regulates hazmat transportation within the territory of the US.