Which colored tube is commonly associated with collecting serum samples?

The red tube, particularly the glass variant, is commonly used for collecting serum samples because it contains no additives that would interfere with the clotting of the blood. When blood is drawn into a red tube, it naturally coagulates, allowing for the separation of serum from the other components of blood after centrifugation. Serum is the liquid portion that remains after the blood has clotted and is essential for various diagnostic tests.

In contrast, lavender tubes typically contain EDTA, an anticoagulant that prevents clotting, making them unsuitable for serum collection. The gray tube often contains sodium fluoride or another additive that preserves glucose levels but also acts as an anticoagulant. The light blue tube contains citrate, which is used primarily for coagulation studies and does not yield serum. Thus, the red tube's properties make it ideal for collecting serum samples, making it the correct choice in this context.