Different medical tubes are color coded according to their use. They are all special tubes used by medical professional and have a universal coding system known to the medical staff. Certain colored tubes contain anticoagulants that prevent the blood from clotting. Once the blood is collected from the body, it will start coagulating immediately unless special measures are taken to prevent the coagulation.
The common colors containing anticoagulants include lavender, green, blue, Lt. Blue and grey. This color codes enable the medical staff to use the right tube when collecting blood for analysis. It also helps differentiate tubes from other phlebotomy ones.