Lavender-Top Tube (EDTA): This tube contains EDTA as an anticoagulant -- used for most hematological procedures. (1) Note: After the tube has been filled with blood, immediately invert the tube several times to prevent coagulation. (1)

THE PURPLE ONE (aka “Lavender”) source: http://geekymedics.com/blood-bottles-guide/ (2).These bottles are generally used for haematology tests where whole blood is required for analysis.
ADDITIVE: contains EDTA (ethylenediaminetetraacetic acid), which acts as a potent anticoagulant by binding to calcium in the blood. EDTA also binds metal ions in the blood and is used in chelation therapy to treat iron, lead or mercury poisoning. Its blood-binding capacity also means it can be labelled with radioisotopes and used as an EDTA scan to test renal glomerular filtration rate.
COMMON TESTS: 

• full blood count (FBC)

• erythrocyte sedimentation rate (ESR)

• blood film for abnormal cells or malaria parasites

• reticulocytes

• red cell folate

• Monospot test for EBV

• HbA1C for diabetic control

• parathyroid hormone (PTH)*

• less commonly used for: ciclosporin/tacrolimus levels, some viral PCR tests, G6PD, ACTH level*, porphyria screen*, plasma metanephrines*, fasting gut hormone screen*

TIPS FOR USE: the purple tube needs inverting about 8 times to mix the sample with the EDTA. About 1ml of blood is sufficient to do a full blood count, but to get an ESR you need a full purple bottle.