Many animals can rapidly change their body colouration and patterning. Rapid colour change provides phenotypic plasticity in varying environmental conditions, but in many species the drivers of such changes are not well known. Here, we explored dynamic colour change in the bluelined goatfish (Upeneichthys lineatus), a temperate marine teleost species that transforms rapidly from a pale buff/white colour to a conspicuous vertically striped red pattern in seconds. Initial observations suggested that rapid colour change in U. lineatus was associated with feeding and may act as a signal to both conspecifics and heterospecifics that are frequently observed to follow feeding goatfish. Through field observations of individual U. lineatus we found that they change colouration from white to the red banded pattern in less than ten seconds. The key driver of rapid colour change in U. lineatus is when the fish are feeding with their heads buried in the sediment. Conspecifics were most likely to be white in colour and adopt searching behaviour, regardless of the focal fish colour or behaviour. Other species of follower fish spent significantly more time following U. lineatus that were displaying dark red stripes when searching or eating, implying the red stripes may be an interspecific signalling mechanism. Our findings indicate that rapid colour change in teleost fish can be used for social communication and may provide U. lineatus with increased protection from predation via a safety in numbers approach.