WHY MUST GAS CANS BE RED?

CODE OF IOWA  214A.15  Gasoline receptacles.

A person shall not place gasoline or any other petroleum product for public use having a flash point below 100 degrees F. into any can, cask, barrel or other similar receptacle having a capacity in excess of one pint unless the same is painted bright red and is plainly marked with the word "gasoline" or with the warning "flammable--keep fire away" in contrasting letters of a height equal to at least one-tenth of the smallest dimension of such container. Gasoline or other petroleum products having a flash point below 100 degrees F. shall not be placed in bottles and plastic containers except those bottles and plastic containers which are approved by the state fire marshal and which are conspicuously posted with such approval. This section shall not apply to vehicle cargo or supply tanks nor to underground storage nor to storage tanks from which such liquids are withdrawn for manufacturing or agricultural purposes, or are loaded into vehicle cargo tanks, but all outlet faucets or valves from such excepted containers shall be suitably tagged to indicate the nature of the product to be withdrawn from such containers.

 http://coolice.legis.state.ia.us/cool-ice/default.asp?category=billinfo&service=iowacode&ga=83&input=214A#214A.15