It could be either red top (to clot it) or Grey top (sodium fluoride or potassium oxalate added) which prevents RBC's from metabolising the glucose in the blood. There is also another one to separate the serum but I forgot the color. It might be "tiger top" or speckled.
I'm 90% sure that a FBS(fasting glucose) is drawn into a SST(serum seperator tube) A.k.a. "tiger top".
vanco trough is drawn in which color tube
Green
Green
REd
Green top tube
Lavender.
red top
blue
lavender
lead levels tube color
Red or lavendar