Receiver biases offer opportunities for the evolution of deception in signalling systems. Many spiders use conspicuous body colouration to lure prey, yet the perceptual basis of such deception remains largely unknown. Here we use knowledge of visual perception in key pollinator groups (bees and flies) to test whether colour-based lures resemble floral signals. We addressed this question at two levels: first according to the spectral reflectance of Australian orb-web spiders and flowers across a broad continental range, and second in reference to polymorphic variation in the species Gasteracantha fornicata. Analysis at the community level supported the hypotheses for broad-scale convergence among spider and flower signals. Moreover, data for G. fornicata indicate that each lure morph presents a signal biased towards the colouration of sympatric flowers. This analysis identified fly- and/or bee-pollinated plants whose flowers are likely to be indistinguishable from each G. fornicata colour morph. Our findings support the hypothesis that deceptive colour-based lures exploit prey preferences for floral resources. Further, the evidence implies a greater role for specific model/mimic relationships over generalised resemblance to flower-like stimuli as a driver of lure colouration and diversity.