Objectives To identify the colour that different groups of observers thought represented bile in a newborn's vomit. Design Questionnaires displaying eight colours (pale yellow to dark green). Setting General practices in Glasgow, postnatal ward and level III special care baby unit in a university teaching hospital, and mother and toddler groups in Glasgow. Participants 47 general practitioners, 29 nurses on the baby unit, 48 midwives, and 41 mothers of babies and infants. Outcome measures Participants indicated which colour would represent bile in a baby's vomit. More than one colour could be chosen. Respondents were also asked to indicate one colour that was the best match for bile. Results When any colour could be chosen, 12 (25%) general practitioners, 1 (3%) nurse on the baby unit, 5 (10%) postnatal midwives, and 23 (56%) parents did not consider green an appropriate colour for a baby's vomit containing bile. Twenty three (49%) general practitioners, 7 (24%) neonatal nurses, 15 (31%) postnatal midwives, and 29 (71%) parents thought yellow was the best colour match. Conclusions There is little agreement about the colour of bile vomit in a newborn. It is more pertinent to ask parents about the colour of vomit rather than whether it contained bile. Many general practitioners and parents do not recognise green as an appropriate colour for bile in the vomit of newborns, which may delay surgical referral. Though yellow vomit does not exclude intestinal obstruction, the presence of green vomiting in a baby is a surgical emergency and requires expeditious referral.