Colour patterning is incredibly important in the animal world – it can influence everything from survival to mate choice. With its growing collection of pigment-patterning mutants, the zebrafish is fast becoming a popular organism in which to study this important process. On p. 3447, Maderspacher and Nüsslein-Volhard analysed four such mutants to investigate stripe formation in zebrafish. In one experiment, they transplanted wild-type cells into mutant embryos lacking one of the two cell types that form stripes:melanophores or xanthophores. Their results show that the juxtaposition of these cell types is both necessary and sufficient to form stripes, as stripes were rescued in tissue patches where both cells were present. From their findings, the authors propose that pigment cell-cell interactions are the driving force behind the formation of the zebrafish's stripes, so ruling out the possibility of prepatterning.