In the hospital environment, a common use of colour is to distinguish between variants of a piece of equipment, for example blood tubes or sizes of cannula. There is little guidance on which colours should be used in constructing a safe and helpful colour code, and the choice is generally left to manufacturers. A rare exception to this is the labelling of syringes in critical care areas, for which clear and well thought out guidance is provided in the UK.1This guidance is backed by the Royal College of Anaesthetists, the Association of Anaesthetists of Great Britain and Ireland, the Royal College of Emergency Medicine, the Intensive Care Society, and the Faculty of Intensive Care Medicine. Similar guidelines are issued in the USA,2 and there is also an ISO (International Organization for Standardization) standard.3 For the individual with normal colour vision, there is little scope for confusion with such labels, as they use a mixture of colour, hatching, and reversal of font and background colour. There is evidence that syringe labelling systems can enhance the safe use of medication.4