The truth about 'the truth about true blue'

It can happen that a single surface S, viewed in normal conditions, looks pure blue (“true blue”) to observer John but looks blue tinged with green to a second observer, Jane, even though both are normal in the sense that they pass the standard psychophysical tests for color vision. Tye (2006a) finds this situation prima facie puzzling, and then offers two different “solutions” to the puzzle.1 The first is that at least one observer misrepresents S’s color because, though normal in the sense explained, she is not a Normal color observer: her color detection system is not operating in the current condition in the way that Mother Nature intended it to operate. His second solution involves the idea that Mother Nature designed our color detection systems to be reliable with respect to the detection of coarse-grained colors (e.g., blue, green, yellow, orange), but our capacity to represent the fine-grained colors (e.g., true blue, blue tinged with green) is an undesigned spandrel. On this second solution, it is consistent with the variation between John and Jane that both represent the color of S in a way that complies with Mother Nature’s intentions: both represent S as exemplifying the coarse-grained color blue, and since (we may assume) S is in fact blue, both represent it veridically. Of course, they also represent fine-grained colors of S, and, according to Tye, at most one of these representations is veridical (Tye says that only God knows which). But at the level of representation for which Mother Nature designed our color detection systems, both John and Jane (qua Normal observers) are reliable detectors