Serum (clot activator) tubes (color dependent on brand; BD is commonly gold but also red, Greiner is red). These tubes have silica particles, which activate clotting. Some also have a gel to separate the serum. Those without the separating gel are potentially more useful in sensitive diagnostic testing. If you’re looking for a protein that isn’t involved in coagulation, this is a good place to start.

Thrombin-based clot activator tubes (orange). Although the silica-coated tubes clot within about 30 minutes, the orange tubes clot within 5. They’re mainly used clinically for tests that are needed especially quickly. However, some of the serum components are a little less stable in these tubes.

Anticoagulant Tubes

This is the category to consider if you need cells or plasma (cell-free liquid which still contains coagulation factors).

EDTA (Purple)

EDTA prevents clotting by chelating calcium, Blood Collection Tubes an essential component of coagulation. This is your basic hematology tube (by which I mean identifying and counting blood cells, blood typing etc). Plasma stored from EDTA blood can also be used to measure most proteins, and genetic material can easily be stored from EDTA buffy coats (the interface between the red cells and the plasma after centrifugation, containing white cells and platelets). Note: these tubes contain either K2EDTA or K3EDTA.