International Standard ISO 20560-1 Safety information for the content of piping systems and tanks — Part 1: Piping systems was intended to replace the variety of regulations and standards across countries and regions. Basic identification colours and warning symbols identify the pipe contents and any hazards.
Pipe markers consists of 4 basic elements:
* Basic identification (background) colour, see table below,  e.g. yellow for hazardous substance
* Name of the substance/content, e.g. NATURAL GAS
* Flow direction indicator arrows, ⇒
* Warning symbols, e.g. GHS symbol
Colours and substances are typically as follows:
International Standard ISO 20560-2 Safety information for the content of piping systems and tanks — Part 2: Tanks, provides a similar colour scheme for tanks.