The hues or the colorimetric purities of a pair of colored targets can be compared with similar precision whether the targets are juxtaposed or fall at well-separated positions in the visual field. This is the case even if the stimuli are 10° apart and fall in opposite hemifields. What could be the neural processes that underlie such comparisons? We are led to ask whether the long-range, white-matter tracts of the brain constitute a neural net (where representations are embodied in the weightings and signs of connections between the nodes of the net) or a communication network (where the same physical substrate carries different information from moment to moment).