Colour vision depends on the presence of photo-receptors with distinct spectral sensitivity and on post-receptoral mechanisms which can compare the relative activation of these receptors. We review recent work on the retinal pathways for colour vision in primates, with emphasis on the cells and pathways involved with processing signals from short-wavelength sensitive (SWS or "blue") cones. We find that there is substantial variability in the distribution of SWS cones when the retinae of different primate species are compared Despite these differences, the synaptic connectivity of SWS cones is very similar in all primates studied so far, The SWS cones are contacted selectively by a depolarising (On-) bipolar cell type, and are biased in their connectivity towards one subset (H2) of horizontal cells. A distinct class of retinal ganglion cell is responsible for transmitting "blue-yellow" cone opponent signals to the brain. The intra-retinal pathways for SWS cone signals are indistinguishable in dichromatic and trichromatic monkeys, suggesting that the SWS chromatic subsystem is an ancient and well-preserved feature in the retina of diurnal primates. (C) 2000 John Wiley & Sons, Inc. Col Res Appl, 26, S112-S117, 2001.