[email protected] would like to know if there is an industry standard for which color tubing is to be used for the main air in a circuit, or cylinders extend & retract, along with e-stops and such.

 

the standard is customized, and stated on the pneumatic plan. for example:

BLUE: AIR SUPPLY
BLACK: MINUS PRESSURE
RED: WORKING
GRAY: HOMING
YELLOW: CONTROL