The cap colors on blood collection tubes tell technicians the tube additives, additive functions and the laboratory tests required. Some collection tubes contain clot activators, which produce serum samples when spun in centrifuges. Other tubes contain anticoagulants, which produce whole blood without a centrifuge and plasma with a centrifuge.
A red or gold blood collection tube stopper indicates the presence of a clot activator, and centrifugation produces serum. The lab tests include chemistry, serology and immunology. A grey stopper indicates lab tests for glucose, blood alcohol and lactic acid. Lavender or pink stoppers produce samples for hematology or blood bank. Technicians rely on blood collection tube stopper colors for other information as well, including specimen size and storage requirements.