For wires that will be 120 208 or 240 volts the following wiring color standards are used.
Ac control wiring colors.
Rc wires are only for air conditioning systems or dual transformer systems.
In other jurisdictions only a few conductor colors are so codified.
Always turn the power off at the air handler and the condenser and make sure there is no voltage at the transformer before proceeding.
These wires only connect to your cooling system.
Red wires specifically rc wires are responsible for 24 hour volt ac power from your transformer.
Ac power comes in many different types based on how many volts the wires will be carrying.
In some jurisdictions all wire colors are specified in legal documents.
Wiring for ac and dc power distribution branch circuits are color coded for identification of individual wires.
Abyc cable wire color codes for yacht boat marine wiring there are multiple colors used for different wires and cables in different regions for ac alternating current single phase three phase and dc direct current for design and installation based on the local codes rules and regulations.
In that case local custom dictates the optional wire colors.