Ships and marine facilities must conform to an international standard for piping systems identification. This is ISO 14726:2008 Ships and marine technology — Identification colours for the content of piping systems.
This is a two-colour banded marking system. The main colour shows what the fluid is being used for. This is on either side of the secondary colour which indicates what the substance actually is. The main colours are as follows:
*  Black - Waste media
*  Blue - Fresh water
*  Brown - Fuel
*  Green – Sea water
*  Grey - Non-flammable gases
*  Maroon - Air and sounding pipes
*  Orange - Oils other than fuels
*  Silver - Steam
*  Red - Fire fighting
*  Violet - Acids, alkalis
*  White - Air in ventilation systems
*  Yellow - Flammable gases