The most important thing on the station besides power, atmospherics keeps people breathing and warm, and also provides some support for thermoelectric power systems. Atmospherics piping is color-coded as follows:
Red: Hot-Loop Piping. Used in thermoelectric engines to indicate piping of gases meant to be very, very hot. Typically heated by the engine, and run through the thermoelectric generator to create power through heat exchange with the cold loop based on the difference between the two.
Blue: Cold-Loop Piping. Used in thermoelectric engines to indicate piping of gases meant to be very, very cold. Typically cooled through heat-exchange piping (ideally into space). More heat-exchange piping means more opportunity to get colder.
Yellow: Primary air lines. These feed good air into the environment.
Cyan: Primary vent lines. These remove bad air from the environment.
White: Intake lines. These inject air into the yellow air loop from sources or from the recycling loop.
Black: Processing lines. These contain air that needs to be processed before the gases can be usable again.