A glucose tolerance test would require a grey vacutainer tube.
A vacutainer tube is a sterile tube used to collect blood. It has a coloured rubber lid which creates a vacuum seal that makes the drawing of the blood easier. A vacutainer tube sometimes contains several substances, such as anticoagulants, depending on the blood tests that will be performed.
They grey vacutainer tube contains sodium fluoride and oxalate. Sodium fluoride blocks the blood enzymes that break down glucose. Oxalate is an anticoagulant, preventing the clotting of the blood.