I am currently working in a busy lvl 2 trauma center in so cal as an ER Tech. One of the requirements of my job was to get a national phlebotomy licence. The proper order of draw starts out with red. Red contains no additives. so to prevent contamination it goes first. Next is blue. The blue tube is for coagulation tests. A lot of people like to draw this one first because it is the only tube that requires a strict 9 to 1 ratio. Technically it should not be drawn first because with the initial needle stick there can be tissue thromboplastin contamination. Verly unlikely unless it is a very traumatic stick. 3rd is the Green tube. It contains heparin which could mess up the blue tube. Then lavender. this is the tube used for CBC's. It contains EDTA which is really bad for all the other tubes. It messes up chemistry tests, pt, ptt, and so on. so Red, Blue, Green, Lavender. On a side note just so you all know the blue tube is the only one that has to be full. The more the better of course but even if the other tubes are only 1/4 full the lab can still run all the standard initial tests.