What are the standard color-coding and functional roles of the dual pneumatic glad-hand connector hoses between a tractor unit and a semi-trailer?

1. RED is the Supply / Emergency line (charges trailer reservoirs and releases spring brakes); BLUE or YELLOW is the Service Control line (transmits service foot brake signals)
2. RED is the drinking water line for the sleeper cab; BLUE is the diesel fuel return line
3. RED is the air conditioning refrigerant line; BLUE is the high-voltage electrical cable
4. Both lines are identical and can be interchanged freely without any functional difference