Why are the Red valves labeled liquid and Blue valves labeled vapor on recovery cylinders? Also who recertifies recovery cylinders?

We’re not sure how the valve colors were selected. To make it even more confusing, not all recovery cylinders have the same valve color coding. Some have the opposite red and blue assignments. Because of this, you should always look for the word “Liquid” on the valve to tell you which port has the liquid dip tube. For cylinder recertification services, check with your wholesaler or refrigerant reclaimer.