Final answer:
The purple color tube is commonly used for a Platelet Count in a blood test because it contains EDTA, an anticoagulant, to preserve platelets.
Step-by-step explanation:
The color tube typically used for a Platelet Count in a blood test is purple. The purple color indicates that the tube contains an anticoagulant, such as EDTA, which prevents the blood from clotting and thus preserves the platelets for accurate counting. Platelet counts are important for assessing various conditions related to the blood's clotting abilities, and purple tubes are also used for other hematological tests.