Pitfall trapping is one of the most commonly used methods of sampling ground-dwelling arthropods. There are many studies on the effect of design of pitfall traps on their capture efficiency but, so far, none on the influence of the colour of the pitfall trap. In this study the abundances of seven invertebrate groups (Apidae, Araneae, Carabidae, Diptera, Formicidae, Isopoda, Vespinae) caught in pitfall traps of different colours (white, yellow, green, brown) at a dense and dry grassland site in Northwestern Germany were determined. White and yellow pitfall traps caught by far the highest numbers of individuals of Apidae, Araneae, Carabidae, Diptera and Formicidae. Isopoda were most abundant in the catches of green and brown traps. Differences among numbers caught were significant for Apidae, Araneae, Carabidae and Diptera. The effect of colour on the catches did not differ significantly between sites. Knowledge of the variation in the catching efficiency of differently coloured pitfall traps is important for designing invertebrate surveys, both from a scientific and ethical point of view.